Why some PDFs are much larger than others
A PDF containing a few pages of text can be very small, while a scanned document with the same page count can be much larger. Images, scan resolution, embedded fonts and repeated document resources all influence the size. Page count alone does not tell you how much a PDF can be compressed.
First, check the limit set by the email service or upload portal you plan to use. Keep an untouched copy of the original document. That gives you a safe reference if a smaller version loses detail you need.
Choose a sensible compression setting
- Open the Compress PDF tool and select your PDF.
- Review the available compression settings and start with the one that best matches how the document will be used.
- Run the compression and download the result.
- Compare the actual file size and visual quality with the original.
Stronger compression may reduce image detail. That can be acceptable for a document that will mainly be read on a phone, but less suitable for a detailed drawing or a file intended for high-quality printing. There is no single setting that is best for every document.
Check more than the file size
Open the compressed PDF and inspect the smallest text, fine lines, screenshots and photographs. Zoom in on scanned pages and check stamps or handwritten notes if they are relevant. Make sure all pages are present and that their orientation is correct.
If you rely on selectable text, links, form fields or digital signatures, check those features too. A document transformation can affect behaviour beyond appearance. Do not assume that a file is suitable for an important submission just because it opens successfully.
When the PDF is still too large
A file that has already been optimised may shrink only a little. Image-heavy scans may offer more room for reduction, but at a quality cost. A compressed result can occasionally be similar in size to the original or even larger, so compare the actual downloaded files.
If the result still exceeds the upload limit, try another available setting and compare again. You can also remove unnecessary pages when appropriate, or split the document if the recipient accepts multiple files. If you control the original source document, exporting it again with suitable image settings may give you a better starting point.
Keep the smallest version that still does the job
The aim is a usable document that meets the recipient's requirements. Keep enough detail for the reader to understand the content, retain the original, and give your final version a clear filename so you send the file you actually checked.