Reduce PDF file size online for free. Shrink scanned and image-heavy PDFs for email, uploads and portals with High, Medium or Low quality, while text stays sharp.
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About this tool
Compress PDF is a free online tool that reduces the file size of a PDF so you can email it, upload it to a portal or store it without running into size limits. Most large PDFs are large because of the images inside them: scanned pages, phone photos and screenshots. The tool shrinks exactly those. For each embedded image it lowers the resolution so the longest side fits the level you choose (2400, 1600 or 1000 pixels) and re-saves it as a JPEG at quality 85, 65 or 40, keeping the new version only if it is actually smaller. Text, fonts and vector graphics are never turned into images, so words stay sharp and selectable at any zoom. Unused objects are removed and internal streams are compressed as a final step. In our own test, a 17.6 MB scanned PDF came out at 4.4 MB on High, 1.27 MB on Medium and 0.29 MB on Low. It works in any browser on Windows, Mac, Android and iPhone, with no app, no sign-up and no watermark. Your file is processed on our server over HTTPS, returned to you, and deleted immediately afterwards.
Select one PDF of up to 100 MB from your computer or phone. If it is password-protected, remove the password first with Unlock PDF.
High keeps images up to 2400 px on their longest side (best for printing), Medium up to 1600 px (email and sharing), and Low up to 1000 px (the smallest file, for strict upload limits).
Each embedded image is resized and re-encoded as JPEG, and kept only if the result is smaller. Unused objects are removed and streams are compressed.
Save the smaller PDF and zoom in on the finest text in any scanned area. If it is still easy to read, you're done. If not, run the original again one level higher.
Only raster images are recompressed. Text, fonts and vector graphics are left as they are, so words stay crisp and selectable.
Scanned and photo-heavy PDFs shrink the most. In our test a 17.6 MB scan dropped to 1.27 MB at Medium, 93% smaller.
Each level has a fixed image-size cap and JPEG quality (2400 px/85, 1600 px/65, 1000 px/40), so you know what you get.
If re-encoding an image wouldn't save space, for example an already-optimised JPEG, the original image is kept.
Typical situations where file size is the problem
Gmail limits attachments to 25 MB and Outlook.com to 20 MB. Scanned contracts and photo-heavy reports often go over.
ExampleA 38 MB scanned rental agreement with 20 pages of 300 DPI scans, compressed at Medium, is usually small enough to attach.
Exam, job, scholarship and visa application portals often limit each document to somewhere between 100 KB and 2 MB.
ExampleA scanned certificate or ID proof that is 4 MB can often be brought under 1 MB at Low quality and still be legible.
Learning platforms such as Moodle or Google Classroom often cap file sizes. Handwritten work photographed with a phone makes very large PDFs.
ExampleTen phone photos of handwritten notes combined into a 45 MB PDF can drop to a few MB at Medium.
Menus, brochures and price lists load faster on mobile when their photos aren't full camera resolution.
ExampleA restaurant menu with 12 food photos straight from a camera loads noticeably faster after compressing at Medium.
Large PDFs are slow to send and download on mobile data, and many people open them on their phone.
ExampleA 20 MB product brochure compressed at Medium downloads in seconds instead of minutes on a 4G connection.
Google Drive's free 15 GB is shared with Gmail and Photos, so years of scanned documents fill it quickly.
ExampleCompressing a folder of scanned bills and statements at High keeps them readable while using a fraction of the space.
What actually affects the final file size
The size cap applies to the longest side of each image. For a full-page A4 scan that works out to about 205 DPI at High, 137 DPI at Medium and 85 DPI at Low. High is fine for office printing; Medium and Low are best kept for on-screen use.
Blank pages, duplicate scans and cover sheets add size for nothing. Delete them before compressing to get a smaller file with no quality loss at all.
Open Remove PagesImages are converted to JPEG, which doesn't support transparency. Logos or stamps with transparent backgrounds can end up on a solid background, so check pages that have them.
Compressing rewrites the file, which invalidates any digital signature already in it. Compress first, then sign.
That is expected. A PDF exported from Word with no images is already compact, and the size mostly comes from embedded fonts, which this tool doesn't change.
JPEG compression is lossy, so detail removed from images can't be restored. Keep the original and always compress a copy.
Read the full compression guide
