Most oversized PDFs are large for one reason: images. Scans, photos and screenshots are often stored at far higher resolution than a screen or an email recipient needs. Compress PDF reduces that image data while leaving text and vector drawings untouched, so the document gets lighter without becoming blurry to read. Choose how far to go, from a gentle clean-up to a much smaller file.
How to use Compress PDF
- Add the PDF you want to shrink.
- Choose a Compression level: Smaller file, Balanced or Higher quality.
- Select Compress PDF.
- Compare the download with the original, zooming in on small text, signatures and photos.
- If it's still too large for a strict limit, try Compress to Target Size.
What each level does
Balanced is the right starting point for email and everyday sharing.
- With Ghostscript: On a server with Ghostscript, the three levels use its standard settings. Smaller file reduces images to about 72 DPI for reading on screen. Balanced uses about 150 DPI, and Higher quality uses about 300 DPI, which suits printing.
- Without Ghostscript, VelloDoc recompresses only the images that exceed each level's resolution threshold and leaves the rest alone.
- Text stays text: Either way, text remains real text and stays crisp at any zoom.
Why some PDFs barely shrink
- Compression works on images, so a PDF made mostly of text, like a contract exported from a word processor, is often close to its smallest size already. Embedded fonts, form data and small vector drawings don't compress much further.
- When nothing would be gained: When the result wouldn't be smaller than your original, VelloDoc returns the original unchanged instead of handing back a bigger file.
- For scanned paperwork where color doesn't matter, Grayscale PDF can reduce the size further.
- When a form sets a hard limit, the pages for 500 KB, 1 MB and 2 MB aim for that size directly, and Optimize PDF for Web helps large files start displaying sooner online.
Checking quality before you send
- What lower resolution costs: Lower resolution is invisible at normal zoom but can soften fine print, stamps and handwritten signatures.
- Zoom to 200 percent: Before sending a compressed file, zoom to 200 percent on the smallest text and on any signature.
- If something is hard to read: If something has become hard to read, run the original again at Higher quality.
- Where to read more: The guide to reducing PDF size explains resolution, JPEG quality and fonts in more depth, including when splitting a document beats compressing it.
When people use Compress PDF
Emailing a scanned contract
Bring a multi-page scan under your email provider's attachment limit while keeping the terms and signatures legible.
Uploading to a job portal
Shrink a CV with embedded photos or certificates so an application system accepts the upload on the first attempt.
Sharing a photo-rich report
Make a report full of high-resolution photos quick to open on phones and cheap to download on slow connections.
Limitations to know
Compress PDF reduces image data only, so text-heavy files shrink very little, and it never removes pages or content. Lower levels soften scanned text and signatures. Compression levels are most effective when the server has Ghostscript. Without it, only oversized images are recompressed.
Compress PDF: common questions
How much smaller will my PDF get?
It depends on what the file contains. Scans and photo-heavy documents often shrink substantially, while text-only files may change very little. Because results vary so widely, trying Balanced and comparing the two files is more reliable than expecting a fixed percentage.
Will compression make text blurry?
No. Text and vector graphics are kept as they are. Only images are resampled and recompressed. Text inside a scan is part of an image, though, so it softens along with the rest of the scanned page at lower settings.
Can I compress a PDF to an exact size?
Use Compress to Target Size. Enter a limit like 1 MB and it tries progressively stronger settings until the file fits.
Does compressing keep the password on a protected PDF?
You can compress a protected file after entering its password, but the compressed copy isn't guaranteed to keep that protection. Check the result, and add a password again with Protect PDF if you need one.
Does compression remove hidden information?
No. It changes image data, not document properties or covered content. Use Remove Metadata or Redact PDF for anything sensitive before sharing.