Drop in a PDF, choose how hard to compress, and download a smaller copy. When it finishes you see the before and after, for example 8.4 MB → 2.1 MB (75% smaller), so you know straight away whether it will fit under an email or upload limit.
Almost all of the weight in a large PDF comes from images: scanned pages, phone photos of receipts, screenshots pasted into a report. This tool works on those images. It re-saves them as JPEG and scales down any that are larger than they need to be, while the text, fonts and vector drawings are left exactly as they were. Text stays crisp and you can still select and search it.
There are three levels. Balanced is the default and suits most scans and reports. Light keeps more detail for diagrams and screenshots, and Strong gets the smallest file when you only need the pages to be readable.
How to compress PDF
- Add your PDF. One file at a time, up to 100 MB. Password-protected files need to be opened with Unlock PDF first.
- Pick a compression level. Light, Balanced or Strong. Start with Balanced unless the file is full of diagrams or screenshots, in which case try Light.
- Compress. The result shows the old size, the new size and the percentage saved, so you can decide whether to try a stronger level.
- Download. The new file keeps your original name with <code>-compressed.pdf</code> on the end, so it will not overwrite the original.
What the three levels actually do
Each level sets two things: the largest an image may be on its longest side, and the JPEG quality it is saved at. Light caps images at 2600 pixels with quality 82. Balanced uses 1800 pixels and quality 68. Strong uses 1200 pixels and quality 50. For a full-page A4 scan that works out to roughly 220, 155 and 100 dpi respectively.
In practice, 220 dpi is close to what most office scanners produce at their normal setting and prints cleanly. 155 dpi reads comfortably on screen and still prints acceptable body text. 100 dpi is fine on a monitor or phone, but small print and fine lines start to soften, so Strong is best kept for documents that will only ever be viewed, not printed.
Images that are already smaller than the cap are not enlarged; they are only re-saved at the level’s quality. An image is replaced only if the new version is at least 10% smaller than the old one, and images under 20 KB or under 64 pixels are skipped altogether, because there is nothing worth saving in them.
Getting a PDF under 1 MB or 2 MB
There is no target-size box where you type 2 MB and get exactly that. Image content varies too much for that to be honest: a page of plain text and a page of photographs at the same resolution can differ in size by a factor of fifty. Instead, work up through the levels. Run Balanced first, check the size shown, and if it is still over the limit put the original back in and run Strong.
If Strong still is not enough, the document is probably just long. A 120-page scanned contract will rarely fit under 2 MB at a readable quality. Use Remove Pages to drop blank or unneeded pages, or Split PDF to send it in two or three parts. Government and university upload portals that cap files at 2 MB or 5 MB usually accept several attachments.
What it will not shrink, and why
Text-only PDFs. A report exported from Word or Google Docs is mostly text and fonts, which are already stored compactly. If compression cannot save at least 2%, you get your original file back unchanged, with a note saying so, rather than a re-saved copy that is no better.
Some image types are deliberately left alone. Images using an indexed (palette) colour table, spot colours, colour-key masks, or a Decode array (common in inverted CMYK scans) cannot be converted to JPEG without the colours shifting, so they are kept as they are. Everything else in the file is still re-saved with compact object streams, and any objects no longer referenced are dropped, which often trims a little extra.
Screenshots and diagrams can soften. JPEG is designed for photos. Flat colours and sharp edges, like a chart or a screenshot of a spreadsheet, can pick up faint blur or speckling around lines, and more so at Strong. For those files Light is the safer choice; check a page or two of the result before you send it.
Questions people actually ask
How do I compress a PDF to under 2 MB for email?
Upload it with the Balanced level and check the size shown on the result. If it is still above 2 MB, run the original again on Strong. If even that is too large, the file is probably long, so remove unneeded pages with Remove Pages or break it into parts with Split PDF and send them separately.
Does compressing a PDF reduce the quality?
Only for the images inside it. Text, fonts and vector graphics are not touched, so they stay sharp and selectable. Scans and photos are re-saved as JPEG and may be scaled down; at Light the difference is hard to see, while at Strong fine print in scans can look softer, especially when printed.
Why did my PDF not get any smaller?
Most likely it contains little or no image data. PDFs exported from Word or similar programs are mainly text, which is already stored efficiently. If compression cannot make the file at least 2% smaller, the original is returned unchanged with a note, rather than a copy that saves nothing.
Which compression level should I use for a scanned document?
Balanced suits most scans: about 155 dpi on an A4 page, which reads well on screen and prints acceptably. Use Light (about 220 dpi) if the document will be printed or has small print. Use Strong (about 100 dpi) only when it will be read on screen and size matters most.
Can I compress a password-protected PDF?
Not directly. An encrypted file has to be opened before its images can be re-saved. Remove the password with Unlock PDF, compress the unlocked copy here, and then add a password again with Protect PDF if the file needs to stay locked when you send it.