Compress PDF Portable Document Format Free Online Secure
Only the images are resampled. Text and vector drawings pass through untouched, so they stay sharp at any zoom.
Compress your file
Drop a PDF here, or choose one.
Your file never leaves this device. Everything runs in your browser.
Nothing uploaded
Two different ways of making a file smaller
There are only two ways to make a file smaller, and they are not alike. The first is to find repetition and write it down once instead of a thousand times — the method of zip, of PNG and of the streams inside a PDF. Nothing is lost; the original comes back bit for bit. The second is to decide that some of the information was not worth keeping, and this is what JPEG does with a photograph: it discards the detail the eye is least likely to miss. The first method has a hard limit, because there is only so much repetition to find. The second has no limit at all — you can go on discarding until nothing recognisable is left — which is why it comes with a quality setting and the first does not.
Where you need it
An attachment that will not fit the mail server's limit; a portal that rejects anything over a few megabytes; a website where every image is downloaded by every visitor; a phone running out of space; an archive of scans where the same document occupies ten times what it needs. Compression is almost always about somebody else's constraint rather than your own preference.
Questions people ask
How small can I go before it starts to look bad?
For photographs, surprisingly far. Dropping a JPEG to around three quarters of its original quality typically removes more than half the file and leaves nothing visible at normal viewing size. Below about half quality, edges start to show a faint halo and flat areas become blotchy, first in skies and skin. The honest test is to look at the result at full size before sending it, since the damage is invisible in a thumbnail and permanent once saved.
Why did compressing my PNG barely help?
Because it was probably already compressed, and because PNG never discards anything. The format finds repetition, and a photograph saved as a PNG has very little repetition to find, which is also why it was so large to begin with. If the image is a photograph, converting it to JPEG will shrink it enormously. If it is a screenshot, a logo or a diagram, it is already near the smallest it can be without losing something.
Does the file lose quality?
It depends on what the two formats can hold. Converting between formats that store the same thing — a PNG to a BMP, a WAV to a FLAC — loses nothing. Converting into a format that throws information away to save space, such as JPEG or MP3, loses a little every time, and converting back does not bring it back. Where a choice exists, this page errs towards keeping the original quality rather than making the smallest file.
Is my file uploaded anywhere?
No. The conversion happens inside your browser, on your own machine; the file never leaves it and there is no server here that could receive it. That is why a large file is limited by your own memory rather than by an upload, and why nothing you convert can appear in anybody's logs — including ours. The audio and video tools do fetch their conversion engine from this site the first time you use them, some thirty megabytes once; after that the work still happens entirely on your machine.
Why people compress PDF files
PDFs have a way of growing. A report with a few photographs reaches fifteen megabytes. A scanned contract of twenty pages comes to forty. A brochure made for printing weighs more than an email server will accept. Meanwhile the places that need the file impose limits: a job application portal that takes five megabytes, a tender system that stops at ten, an email attachment limit of twenty. When a document is too heavy for where it has to go, the answer is to compress the PDF so that it fits, without making the pages unreadable.
The need turns up in ordinary life constantly. An invoice with a logo and a scanned signature. A CV with a portrait photograph. A school assignment with pictures. A set of receipts photographed on a phone and bundled together. Each of these can be much smaller than it is, because most of the weight is in a few images that were saved at a higher quality than any screen or office printer can show.
This page lets you compress PDF files entirely in your browser. Your document is not uploaded to a server, which matters for contracts, medical papers, payslips and anything else private. Below you will find exactly what the compression touches, what it leaves alone, which documents shrink a great deal and which hardly at all, and how to pick a setting.
What the compression touches
Only the images are resampled
When you compress a PDF here, only the images inside it are changed. Each picture is resampled: redrawn with fewer pixels, so that it takes up less space. That is where almost all the weight in a heavy PDF lives, so reducing the images reduces the file. Everything else is passed through exactly as it was.
You choose how far to go
You pick a resolution, measured in dpi, which is dots per inch. Images that are above the chosen dpi are reduced to it; images that are already at or below it are left alone. A higher setting keeps more detail and shrinks the file less; a lower one shrinks it more and softens the pictures. This gives you direct control over the trade-off between size and sharpness.
What dpi means in practice
As a rough guide, one hundred and fifty dpi is plenty for reading on a screen and for ordinary office printing. Three hundred dpi is the usual standard for good print quality. Seventy-two to one hundred dpi is acceptable for a quick look on a phone. If you are unsure, start with a moderate setting, check the result, and go lower only if you need the file smaller.
What is left untouched
Text and vector drawings
All text and vector artwork pass through exactly as they were. Text in a PDF is stored as characters, not pictures, and vector drawings such as charts, logos and lines are stored as shapes. Neither depends on resolution, so neither needs resampling, and neither is touched. They stay sharp at any zoom, and your text remains selectable and searchable.
Page structure
The page count, the page sizes and the order of everything stay exactly as they were. Nothing is added, removed or rearranged. The document you get back has the same pages in the same order, with only its pictures lighter.
Why this approach is safe
Some tools squeeze a PDF by turning every page into a picture, which makes the text unselectable and often blurry. Resampling only the images avoids that. Your document stays a real document with real text, and the only change is to the heavy part.
Which PDFs shrink, and which do not
Documents full of images shrink a lot
PDFs made from scans, photographs, brochures and presentations with pictures can shrink dramatically, often to a fraction of their size, because they are mostly image data. A forty-megabyte scan may drop to four or five at a sensible setting, and still read perfectly well.
Mostly-text PDFs barely change
A PDF that is mostly text will barely shrink, because there is nothing to resample. A hundred pages of typed text may be only a few hundred kilobytes already, and no amount of compression can make characters smaller. If your file is already small and mostly text, the right answer is that it does not need to be compressed.
How to tell which kind you have
Check the file size against the page count. If a PDF has ten pages and weighs ten megabytes, it is heavy with images and will shrink well. If it has a hundred pages and weighs one megabyte, it is almost all text, and compressing will do very little.
What a PDF contains, and where the weight comes from
A PDF is a container for pages, and each page can hold three kinds of things: text, vector drawings and images. Text is stored as characters with a position and a font. Vector drawings, such as lines, shapes and charts, are stored as instructions for drawing them. Images are stored as grids of coloured dots. Of the three, images are by far the heaviest, because a grid of dots needs data for every dot, while text and drawings are described very compactly.
That is why it is so effective to compress PDF files by working on the images alone. In a typical heavy PDF, ninety-five per cent of the weight can be the pictures. Reducing those, and leaving everything else exactly as it was, gives the largest saving for the smallest cost to the document. Your words and drawings are not blurred, because they were never pixels in the first place.
Resampling, in plain words
To resample an image is to redraw it with fewer dots. If a photograph in your PDF has 3000 dots across a space that prints five inches wide, it has 600 dots per inch, far more than a printer or screen can use. Resampling it to 150 dots per inch cuts the dots to a sixteenth, while the picture still looks the same at that size. This is the heart of what it means to compress PDF files properly.
Scans, photographs and presentations
Three kinds of document benefit most when you compress PDF files. Scanned paperwork is nothing but pictures of pages, often at a very high resolution chosen by the scanner. Documents with photographs, such as brochures, reports and catalogues, carry full-size originals. Presentations exported to PDF contain images that were inserted at many times the size they are shown.
For scans, there is a useful rule: if a scan is crisp at one hundred and fifty dpi on screen, the extra detail of a three-hundred or six-hundred dpi scan is wasted weight. When you compress PDF files made from scans, a moderate dpi usually shrinks them to a fifth or a tenth of their size with no loss you can see at reading size.
Scans of text
A scan of a typed page is a picture of text, not text itself. Reducing the resolution too far makes the letters soft and hard to read, so for scanned text be a little more generous with the dpi, and zoom in on the result to check that the smallest print is legible.
What compression cannot do
It cannot shrink what is already small. A mostly-text PDF has no heavy images, and nothing will make it meaningfully lighter. It cannot turn a scan into searchable text; that would need text recognition, a different job. It cannot restore detail once images have been reduced. And it cannot change the page count: if a file is too heavy because it has too many pages, the remedy is to remove or extract pages, not to compress.
Sometimes the file is the right size already
If you compress PDF files and the saving is tiny, the file may simply be as light as it can sensibly be. There is no failure in that. It means the document is mostly text, or its images are already at a low resolution, and the sensible conclusion is to send it as it is.
How to compress PDF files here
Add your PDF
Drop the PDF onto the page or pick it from your device. It is read inside your browser and is not uploaded.
Pick a resolution
Choose a dpi that suits the use. For documents that will be read on screen or sent by email, a moderate setting is usually right. For anything that will be printed with care, keep it higher.
Compress and check
Press the button and download the smaller PDF. Compare the sizes, then open it and look at the pages with images. If they look fine at the size you will use, you are done; if they look too soft, repeat from the original with a higher setting.
Tips for good results
Always compress from the original
Each round of resampling loses a little detail. Compress once, from your original file, rather than repeatedly shrinking an already compressed copy.
Keep the original
Never delete your full-quality PDF. You cannot get detail back later, and the original is the one to use if you ever need to print at high quality.
Try smaller steps first
If you have a size limit, start with a moderate setting and check the size. If it is still too big, go a step lower. Taking it in steps gives you the largest size that fits.
Questions people ask before compressing
Will my text become blurry?
No. Text and vector drawings are not touched, so they stay sharp at any zoom. Only images are reduced.
Why did my PDF barely shrink?
Because it is mostly text. There are no large images to resample, so there is little to save.
Does it change the page order or count?
No. The page count, sizes and order stay as they were.
Is my file uploaded?
No. Everything runs in your browser and the file never leaves your device.
Who needs to compress PDF files
Job seekers and applicants
Portals often limit attachments to a few megabytes. Compressing a CV or a portfolio PDF gets it under the limit.
Offices and small businesses
Scanned paperwork and invoices with logos add up. Compressing before archiving or emailing saves storage and bandwidth.
Students and researchers
Assignments with figures and photographs are often too big for upload forms. A moderate compression makes them fit.
Common mistakes
Setting the dpi too low
Going too far makes images soft and small text in pictures illegible. Check the result before you send it.
Compressing a mostly-text file
It will not shrink, and there is nothing wrong. Leave it as it is.
Deleting the original
You cannot restore detail later. Keep the full-quality file.
Related tools
If a PDF is too long as well as too big, remove pages from PDF or extract the pages you need. To join several smaller files, merge PDF files, and to cut a big one into parts, split PDF. If the images are the issue, shrink them at the source with compress JPG or compress PNG before putting them into a document with JPG to PDF. When the file is the right size, you can protect it with a password.
When to compress PDF files, and when not to
Compressing is right when a PDF is heavy because of images and has to fit somewhere: an email, a portal, a form, a phone. It is the wrong move for a document that will be printed at the highest quality, such as a poster or a photo book, where you should keep the original for the printer. And it is pointless for a mostly-text file that is already small.
For the common cases, such as scans, applications, reports with photographs and presentations, it is quick, private and effective to compress PDF files in the browser. Your original is never changed, so you can come back and compress PDF files again at a different setting whenever you like.
Choosing between compressing and trimming
If a file is too big, you have two levers: make the images lighter, or send fewer pages. Often both help. Before you compress PDF files, ask whether every page needs to go. Dropping a cover sheet, a blank page or an unrelated annex reduces the file before any resampling. After that, a moderate compression finishes the job.
Compressing before you merge
If you plan to join several PDFs into one, compress the heavy ones first and merge afterwards. That way you know what each part contributes, and the merged file inherits their lightness. Doing it the other way round works too, but you cannot tune the settings for each source.
Large files and slow devices
Everything runs on your own device, so very large PDFs depend on its memory. A twenty-megabyte file is no trouble for a modern computer. A very large scan may be slow on an older phone. If it struggles, give the browser a moment and avoid switching to other apps while it works. For huge files, split them, compress PDF parts separately and merge them again.
Checking the result properly
After you compress PDF files, open the result and look at the pages with the biggest images, at the size you will actually use. Zoomed-in views always look soft; what matters is how it looks at reading size. If it looks right there, the compression has done its job, and you can stop.
Your file stays on your device
The compression happens locally. Your PDF is read by your own browser, its images are reduced there and the file is handed back. Nothing is uploaded, so there is no copy on a server and no one else who could see the contents. For contracts, financial documents and personal papers, that is the safe way to compress PDF files.
A worked example
Say you have a scanned rental agreement of twelve pages and 28 megabytes, and the landlord's portal accepts at most 5. You drop the file here, choose a moderate dpi and press the button. You download a PDF of about three megabytes. You scroll through it: the text in the scan is still perfectly legible, the pages are in order and the page count is unchanged. You upload it and the portal accepts it.
A simple routine to compress PDF files well
Start by deciding where the PDF is going and how big it may be. Look at the file: is it heavy because of images? Remove any pages that do not need to go. Then compress PDF files once, from the original, with a moderate dpi, and look at the result at the size it will be read. If it is still too big, take one step lower from the original, not from the copy. When you compress PDF files in this way, you end with the largest document that fits, which is exactly what you want. It takes a minute, and it works whether you compress PDF files once a month or every day.
Finally, save the compressed file under a clear name next to the original, so there is never any doubt about which is which. Send the light one; keep the heavy one for the day you need full quality.
Before you close the page
Check that you downloaded the smaller file, that the pages with images still look fine, and that you kept the original.
Summary
To compress PDF files here, drop the file, choose a dpi and download the result. Only the images are resampled, and only those above the chosen dpi are touched. Text and vector drawings pass through untouched, so they stay sharp at any zoom, and page count, sizes and order are kept. A PDF that is mostly text will barely shrink. Nothing leaves your device.