Why PDFs get large, what compression actually changes, and step-by-step ways to get under email and portal size limits while keeping text sharp.
Government portals, job applications and email providers all have upload limits — often 2 MB, 1 MB or even 200 KB. A scanned document from a phone can easily be 10 MB. Compressing a PDF is the fix, but done carelessly it turns text into blurry mush. Here is how to do it properly.
Why is my PDF so large?
Text in a PDF is tiny — a hundred pages of plain text might be a few hundred kilobytes. Almost all of the size comes from images:
- Scanned pages are stored as full-page photos, often at 300–600 DPI.
- Phone camera photos inserted into a PDF keep their original 12–50 megapixel resolution.
- Some PDFs embed complete font files for every font used.
- Files exported from design tools may contain hidden layers and duplicate images.
What compression changes
A good PDF compressor mostly works on the images inside the file. It lowers their resolution (for example from 600 DPI to 150 DPI) and re-encodes them with stronger JPEG compression. Text and vector graphics are left as they are, so they stay sharp.
| Resolution | Good for |
|---|---|
| 72–96 DPI | Viewing on screen only; smallest files |
| 150 DPI | Most uploads and email; text in scans stays readable |
| 300 DPI | Printing; files stay large |
Step-by-step
- Open the PDF compressor and add your file.
- Start with a medium compression level and check the result size.
- Zoom in to 100% on the smallest text, signatures and stamps. If they are still clear, you are done.
- If the file is still too big, try the stronger level — then check again.
- If it is still too big, split the PDF and remove pages that are not required, or compress the original scans before making the PDF.
Runs in your browser — your document is not uploaded to any server.
Compress a PDF →Tips for scanned documents
- Scan in grayscale or black-and-white instead of colour when colour is not needed. This alone can cut the size by half or more.
- Crop away the table or background around the paper before converting.
- Use one PDF per document. A combined 20-page file is harder to get under a limit than five 4-page files.
Why privacy matters for PDF tools
The PDFs people compress are often ID cards, bank statements, mark sheets and contracts. Many online PDF tools upload your file to their servers to process it. Browser-based tools process the file on your own device, so the document never leaves your computer or phone.
Frequently asked questions
Does compressing a PDF reduce quality?
It reduces the quality of images inside the PDF. Text stays sharp. With moderate settings, the difference is usually invisible on screen.
Can I compress a password-protected PDF?
You will normally need to remove the password first, compress, and then add the password again.
Related tools
More guides
Spotted a mistake? Email support@cygnatrix.com and we will correct it. See our editorial policy.