PDF Compressor
Shrink PDF file size. Uses Ghostscript when available for deep compression with image quality control; falls back to FPDI re-encoding (5-15% savings) otherwise.
- Free · no sign-up
- Instant results
- Privacy-friendly
Ghostscript not detected on this server — using FPDI re-encode fallback (typical 5-15% savings). Install Ghostscript for deeper compression with image-quality presets.
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What makes a PDF large
Almost always images. Text and vector graphics are compact — a hundred pages of text is often under a megabyte. A single photograph placed at camera resolution can be several megabytes on its own, and a PDF stores that full resolution regardless of how small the image appears on the page.
This is why scanned documents are the worst offenders. Every page is a photograph, frequently captured at 300 or 600 DPI, so a twenty-page scan easily reaches 50 MB while the same document typed out would be a fraction of that. Embedded fonts add a little, and duplicated resources add more, but images are the thing worth attacking.
Choosing a preset
The presets set how aggressively images are downsampled, which is the main lever on size:
- Screen — targets roughly 72 DPI. Smallest files by a wide margin. Right for email attachments and anything read on a display, but images will look soft if printed.
- Ebook — around 150 DPI. The best general-purpose choice: substantial savings while staying acceptable for casual printing.
- Printer — around 300 DPI. Modest savings, print quality preserved. Use when the document will genuinely be printed and read closely.
Results vary a lot, and sometimes there is nothing to gain
An image-heavy or scanned PDF can shrink by 70 to 90 percent. A text-only PDF may barely change, and a PDF that was already compressed will sometimes not shrink at all — the savings have already been taken, and there is no second helping.
A file can even grow slightly. Re-encoding is not free, and if the original used more efficient compression than the re-encode produces, the result can be marginally larger. When that happens, keep the original.
Compression is also lossy for images and permanent. Keep the source file. If you need to edit the document later, edit the original and compress a fresh copy rather than working from a compressed version, since repeated cycles accumulate visible degradation.
What compression does not do
It does not make a scanned page searchable. A scan is a picture of text, and compressing it leaves it a picture. To select or search the words you need OCR, which recognises the characters and adds a text layer behind the image.
It also does not remove content. Compression reduces how the file is stored, not what it contains — so anything hidden in the document, such as metadata, annotations or content beneath a black box drawn over it, is still there afterwards. Redaction is a separate operation that genuinely removes the underlying data, and confusing the two has caused a number of well-publicised leaks.
Getting a smaller file before you compress
The best savings usually come earlier in the process. Resize images to the size they actually appear at before placing them, rather than dropping in 4000-pixel photos and scaling them down in the layout — the full resolution is still stored either way.
When scanning, 200 to 300 DPI is plenty for ordinary documents; 600 DPI quadruples the data for detail that is invisible in normal reading. Scanning text in greyscale or black and white instead of colour also cuts size dramatically. And if a document is only large because it has many pages, splitting it may serve your reader better than compressing it into softness.