Why PDF files get so large
PDF files grow large primarily because of images. A document with high-resolution photographs, scanned pages, or embedded graphics can easily reach 20–100 MB, even if the text content is minimal. Each scanned page from a flatbed scanner is typically saved at 300 DPI or higher, which produces image data that far exceeds what is needed for screen viewing or standard printing.
Method 1: Compress a PDF online (any device, no install)
The fastest method is a browser-based compression tool. Go to signvert.com/tools/resize-file, upload your PDF, adjust the quality slider, and download the compressed result. The tool processes your file locally in the browser — nothing is uploaded to a server. For most documents, a quality setting of 70–80% reduces file size by 40–70% with no visible quality loss.
Method 2: Compress a PDF on Mac using Preview
Open the PDF in Preview, go to File → Export as PDF, and in the Quartz Filter dropdown, select "Reduce File Size". This applies Apple's built-in compression filter. The limitation is that the filter can be aggressive and sometimes over-compresses images. For finer control, the online method above gives you a quality slider.
Method 3: Compress a PDF on Windows
On Windows, open the PDF in Edge browser, press Ctrl+P, select "Microsoft Print to PDF" as the printer, and click Print. This re-renders the PDF and often produces a smaller file. For more control, the free version of PDF24 Creator offers a compression tool with quality settings.
Method 4: Compress a PDF on iPhone or Android
On mobile, use Signvert directly in Safari (iPhone) or Chrome (Android). The process is identical to the desktop online method — open the tool, upload the PDF, adjust quality, and download the compressed result.
How much can you reduce a PDF's file size?
| Document type | Typical reduction |
|---|---|
| Scanned document (300 DPI) | 60–80% |
| Photo-heavy brochure or report | 40–70% |
| Mixed text and images | 20–50% |
| Text-only document | 5–15% |
Frequently asked questions
Will compressing a PDF affect the text quality?
No. PDF compression tools reduce the resolution of embedded images, not the text. Text in PDFs is stored as vector data, which is not affected by image compression. The text will remain sharp at any zoom level.
Can I compress a password-protected PDF?
Most compression tools require the PDF to be unlocked before compression. If the PDF has a permissions password, you will need to remove it first using the owner password.