Why Is My PDF So Large? Common Causes and How to Fix Them

A ten-page report should be a few hundred kilobytes, yet PDFs regularly come out at 20, 50 or 100 MB. The size almost always comes from one of a handful of things inside the file. Start by dropping it into the PDF Size Analyzer to see its size per page and what it contains.

1. Scanned pages

A scanner or scanning app saves each page as a picture, often at high resolution and in colour. Ten scanned pages can easily be 10–30 MB. Fix: scan in greyscale at 200–300 DPI for documents, or run the finished PDF through Compress PDF, which brings the page images down to a sensible resolution.

2. Full-size photos

A photo straight from a phone is often 3–6 MB and far more pixels than a page needs. Insert ten of them into Word or a design tool and export to PDF, and the PDF carries every one at full size. Fix: shrink the photos first with the Image Compressor or Image Resizer, then insert them, or compress the finished PDF.

3. The export settings

Most programs can save a smaller PDF if you ask. In Word for Windows, choose File → Save As → PDF and select Minimum size (publishing online). On a Mac, open the PDF in Preview, choose File → Export, and set the Quartz Filter to Reduce File Size. Re-exporting from the original document usually gives the best quality for the size.

4. Embedded fonts

PDFs carry the fonts they use so the document looks the same everywhere. A few decorative or Asian-language fonts, embedded in full rather than just the letters used, can add several megabytes. Fix: stick to common fonts, or let your export settings embed only the characters used (often called subsetting).

5. Extra pages and attachments

Blank pages, duplicated appendices, high-resolution covers and files attached inside the PDF all add weight. Fix: delete what isn't needed with the PDF Page Remover, or keep only the pages you need with the Page Extractor.

6. Repeated edits

Some editors save changes by adding to the end of the file instead of rewriting it, so a PDF that has been edited many times can carry old versions inside. Fix: use Save As (or Export) to write a fresh copy, rather than Save.

Need a specific size?

Upload portals often cap files at a fixed size. Compress straight to the limit with Compress PDF to 200 KB, 500 KB or 1 MB. For email limits and more ways to cut size, see how to reduce PDF file size.