How to use PDF Compressor
- 1Drop in a PDF — it is read on your device, not uploaded
- 2Choose Light to keep text selectable, or Strong for a much smaller file
- 3In Strong mode, set the JPEG quality for the rasterised pages
- 4Run the compression and compare the before and after sizes
- 5Download the result
What PDF Compressor does
A PDF's size is almost never the text. Written characters are a few bytes each; what fills a large file is embedded images, subset fonts and the structural overhead of how objects are stored. A ten-megabyte document is usually one scanned page repeated, or a report with photographs placed at full camera resolution.
That means there are two genuinely different ways to compress one, and they are not variations of the same setting. You can repack the file's internal structure without touching its content, which is safe and gives a modest saving. Or you can re-render each page as a picture, which shrinks image-heavy documents dramatically and destroys the text layer in the process.
When to use it
- Uploads that reject large files
- Application portals and government forms frequently cap PDFs at 2 MB or 5 MB. Strong mode reliably gets scanned documents under those limits when Light mode cannot.
- Scanned documents
- A scan is already a picture, so it has no text layer to lose. That makes Strong mode the obvious choice — you give up nothing and often shrink the file several-fold.
- Reports with photographs
- Images placed at full camera resolution are stored at that resolution even though the page prints at a fraction of it. Rasterising at screen or high scale drops the waste.
- Anything that must stay searchable
- Contracts, papers and reference documents need selectable text. Light mode is the only safe option here, and it is lossless — the content is untouched.
PDF Compressor settings explained
- Light — keeps text selectable
- Rewrites the document structure with compressed object streams. Completely lossless: every page, font and image is preserved exactly, and the text stays selectable, searchable and copyable. The saving is modest, and near zero on image-heavy files.
- Strong — rasterises pages
- Re-renders every page as a JPEG and rebuilds the PDF from those pictures. Shrinks image-heavy documents dramatically, but the text becomes part of the image — no longer selectable, searchable, or readable by a screen reader.
- JPEG quality
- Applies to Strong mode only. Lower values shrink the file and introduce visible artefacts around text edges, where JPEG compression is at its weakest. Around 60% is usually the balance point for a document.
- Output
- A single file named freetools-compressed.pdf. In Strong mode the result reports how many pages were rasterised, so you can confirm nothing was dropped.
Light or Strong
| Mode | Text stays selectable | Lossless | Typical saving |
|---|---|---|---|
| Light | Yes | Yes | Modest, near zero on scans |
| Strong | No | No | Large on image-heavy files |
Limits and what to expect
- Strong mode is irreversible: once pages are rasterised the text layer cannot be recovered from the output.
- Light mode cannot recompress embedded images, so it barely helps on a scanned document.
- Rasterising loses interactive content — form fields, links and annotations do not survive Strong mode.
- Every page is rendered in the browser, so a long document takes noticeably longer in Strong mode.
- Documents requiring a password to open cannot be read; permission-restricted ones are fine.
Troubleshooting
- Light mode barely changed the size
- The file's bulk is embedded images, which Light mode deliberately does not touch. That is what makes it lossless. Use Strong mode if the saving matters more than keeping the text selectable.
- I can no longer select the text
- The document was compressed in Strong mode, which converts each page to a picture. There is no way back from the output — recompress the original in Light mode instead, or run the Strong result through OCR elsewhere to rebuild a text layer.
- The text looks fuzzy after compressing
- JPEG is designed for photographs and handles the hard black-on-white edges of text poorly. Raise the JPEG quality, or use a higher render scale so there are more pixels describing each character.
- "That file could not be read as a PDF"
- The document is corrupt or needs a password to open. Files that merely restrict printing or copying are handled normally; one that will not open without a password has to be unlocked in the application that produced it.
Your files and your privacy
Both modes run entirely in the browser: Light rewrites the document with a PDF library on your device, and Strong renders each page to a canvas locally before rebuilding the file. Nothing is uploaded at any stage. Given that the documents people most often need to compress are scans of identity papers and financial statements, that is the difference that matters here.
What to use next
FAQ
Why did my PDF barely get smaller?
You used Light mode on a document whose size is mostly embedded images. Light mode compresses the file's internal structure and deliberately leaves content untouched, which is what makes it lossless. On a scan, almost the entire file is image data, so there is nothing for it to reclaim.
Will compressing make my text unsearchable?
Only in Strong mode. Light mode preserves the text layer exactly, so the document stays selectable, searchable and accessible. Strong mode turns each page into a picture, and the text becomes pixels — which is fine for a scan that never had a text layer, and a real loss for a document that did.
How do I get a PDF under 2 MB?
Use Strong mode and lower the JPEG quality until it fits. For a scanned document this almost always works and costs nothing, since a scan has no text layer to lose. For a document with real text, consider whether removing pages or images would be better than rasterising the whole thing.
Is Strong mode reversible?
No. Once a page is rendered to an image, the original text objects and fonts are gone from the output. Keep your original file — the tool never modifies it — so you can always go back and compress differently.
Can I compress a password-protected PDF?
Only if the password restricts permissions rather than opening. Files that just prevent printing or copying are read fine. A file that demands a password to open must be unlocked first in the program that created it.
Is my document uploaded to a server?
No. The PDF is read, rendered and rebuilt inside your browser tab. Nothing is transmitted, stored or logged, and the tool continues to work with the network disconnected.