How to compress a PDF
A PDF is usually heavy because of its pictures, not its text. Compress PDF works on the pictures at the level you choose, optimizes the fonts and the file structure, and never rewrites the text. All three levels are free.
Step by step
- Open Compress PDF and choose or drop your PDF.
- Pick a level: Lossless re-encodes no picture; Recommended re-encodes the larger pictures as JPG, resampled from the size they are displayed at on the page, at 150 dpi; Extreme does the same at 72 dpi, for the smallest file.
- Select "Compress PDF", then download the result. If a level cannot make the file smaller, you get a message instead of a file.
What every level does
At every level, fonts and the file structure are optimized the same way: Type 1 fonts are converted to the compact CFF format, and the result is checked to make sure every glyph is still there; duplicate TrueType subsets are merged, and the structure is repacked.
Which level to choose
| Your PDF | Choose |
|---|---|
| Text, a report, a form, a contract | Lossless first: in our test, a 15-page research paper became 35.4% smaller, and every page rendered pixel-identical to the original in two independent renderers. |
| A document with photos, to send by email | Recommended: the same research paper became 40.6% smaller, and a PDF of six photos 15.2% smaller. |
| A photo-heavy PDF that must be as small as possible | Extreme: the PDF of six photos became 78.8% smaller (only 0.1% with Lossless). |
These figures come from our test of September 23, 2026. Results depend on what the PDF holds: from 0.1% to 78.8% in that test. No level promises a target size such as 1 MB.
What compression does not change
- The text is never rewritten, so it stays as sharp and as searchable as it was. Vector drawings are not rewritten either.
- A picture that needs no resizing is replaced only when its JPG is clearly smaller.
- CMYK and indexed-color pictures, image masks, and pictures with a color-key mask are left as they are; a transparent picture keeps its transparency.
Where your PDF goes
Compress PDF works on our own pdf-tools server, for files up to 200 MB. Up to 4 MB, the file passes through our site and the service's temporary folder is deleted when the request ends. A larger file is uploaded in chunks: the upload is deleted once the compressed file is ready, and that file as soon as this page has received it in full, or after 15 minutes at the latest.
Above 200 MB, a phone or tablet refuses the file; a computer runs a lighter, structure-only optimization in the browser, within the limit the tool page shows. Each network may compress a limited number of PDFs per hour and per day.
Frequently asked questions
Does compressing a PDF lower the quality of the text?
No. The text is not rewritten at any level. Only pictures can change, and only with Recommended or Extreme.
Why did my PDF hardly get smaller?
Its weight may come from text, fonts, or pictures that are already well compressed. Try Recommended or Extreme: they are the levels that act on pictures, which is what a scanned PDF is made of.
Can I compress a password-protected PDF?
Yes, if it opens without a password. A PDF that asks for a password to open is refused, with a message pointing to Unlock PDF; a PDF that opens freely but restricts printing or copying is compressed like any other file.
Can I compress several PDFs at once?
No, one PDF at a time. To get one smaller file from several, merge them with Merge PDF first, then compress the result.
Can I compress a PDF on my phone?
Yes, files up to 200 MB, with the same three levels.