Free Compress PDF
Reduce PDF file size with lossless optimization or screen, balanced and print raster presets. Compare result bytes before you share. No uploads.
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How to compress a PDF to a smaller file size
Choose a lossless rewrite that keeps text selectable or raster presets that turn pages into JPEG images for much smaller scans.
- Choose the PDF to compress. Only the first file is processed unless you tick the option to compress every chosen PDF.
- Pick a compression level: Lossless structure optimization, or a raster preset at 96, 144 or 200 DPI.
- Leave Pages / ranges blank to keep every page, or enter a range to keep only some pages.
- Select Process & download, then compare originalBytes and resultBytes in the report shown below the buttons.
- Open the result and zoom in on small text before you replace or send the original.
When to compress a PDF
Email services, school portals and government forms often set an upload limit, commonly somewhere between 2 MB and 25 MB. Scanned documents and PDFs exported from phones are frequent offenders, because each page is a large photo. Compressing brings them under the limit without retyping anything.
A smaller PDF also opens faster on phones and takes less space in shared drives. If you only need part of a document, compressing a page range keeps just those pages, which can cut the size further than any quality setting.
When you have a batch of scans, such as a month of receipts, choose them all and tick the option to compress every chosen PDF. Each file is compressed separately with the same settings and the results arrive together in one ZIP.
Worked example: a 10-page scanned letter
Suppose scan.pdf has 10 Letter-size pages, which are 612 by 792 points, or 8.5 by 11 inches. With Raster: balanced, each page is rendered at 144 DPI, so it becomes 8.5 x 144 = 1224 by 11 x 144 = 1584 pixels and is saved as a JPEG at 75% quality. Screen quality at 96 DPI gives 816 by 1056 pixels, which is about 44% of the pixels of the balanced setting. Print at 200 DPI gives 1700 by 2200 pixels.
Say the original is 18,400,000 bytes and the balanced result is 2,950,000 bytes. The saving is (18,400,000 - 2,950,000) / 18,400,000 x 100 = 84.0%. Your own numbers depend on the scan, so read the originalBytes and resultBytes values in the report rather than assuming a figure. The file downloads as 01-scan-compress.pdf.
How each compression level works
Lossless structure optimization copies the selected pages into a fresh PDF with the pdf-lib library and saves it with compressed object streams. Text, fonts, vector drawings and embedded images are kept as they are, so the saving comes only from tidier file structure and dropped unused objects. It may be small, or none at all.
The raster presets render every selected page in your browser at the preset resolution, encode it as a JPEG and place that image on a new page of the same physical size. This replaces whatever was on the page, so text becomes unselectable and links, form fields, bookmarks and metadata are removed. In exchange, scanned and photo-heavy pages usually shrink a lot. Each rendered page is limited to 16 megapixels and the output to 100 MB.
Common mistakes to avoid
Using a raster preset on a text document is the classic mistake. A report exported from a word processor is mostly text and can grow when every page becomes a picture, and it loses search and copy. Start with the lossless option for such files.
The second mistake is skipping the visual check. Screen quality is fine for reading on a monitor but can blur small print, signatures and fine tables when printed, so zoom in before you send. Also note that compressing removes any digital signature, and that encrypted files need an authorized unlocked copy first.
Useful tips and limitations
- Try Lossless structure optimization first for documents with real text. Use raster presets mainly for scanned pages and photos.
- If the result is larger than the original, keep the original; compression is never forced on you.
- Combine options: compress only the pages you need by entering a range such as 1-3,7.
- For a form that requires printing, the print preset at 200 DPI keeps small text more legible than screen quality.
Common questions
Will Compress PDF keep my text selectable?
Lossless structure optimization keeps text, fonts and vector graphics. The raster presets turn each page into a JPEG image, so text is no longer selectable or searchable.
Which Compress PDF preset gives the smallest file?
Raster: screen quality (96 DPI) at 55% JPEG quality usually gives the smallest result, followed by balanced (144 DPI, 75%) and print (200 DPI, 88%). Results depend on the content.
Why is my compressed PDF bigger than the original?
Some PDFs are already well optimized, and turning text pages into images can add bytes. The report shows both sizes so you can keep whichever file is smaller.
Does Compress PDF upload my document to a server?
No. Rendering, JPEG encoding and saving all run in your browser. The PDF rendering engine loads from this website when needed.
Can Compress PDF reach an exact file size?
No. It offers fixed presets and reports the actual result size. Try a lower preset or fewer pages if the file is still above your limit.
Can Compress PDF process several files in one run?
Yes. Choose up to 20 PDFs and tick the option to compress every chosen PDF. The compressed files download together in a ZIP with a processing report.
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