"File too large to attach." Almost everyone has hit that email error at some point, usually right when a deadline is closing in. Large PDFs are usually the result of high-resolution scanned images, embedded fonts, or uncompressed photos stacked page after page. The fix is not to lower your standards on the document it is to compress it properly, so the file shrinks without the text turning blurry or the images looking pixelated.
What Actually Makes a PDF File Large
Text itself takes up very little space in a PDF. The size almost always comes from embedded images scanned pages, high-resolution photos, or screenshots pasted into the document. Fonts can also add weight if multiple font families are embedded rather than referenced. Understanding this helps you know where the savings will actually come from during compression.
Scanned Documents
Each scanned page is essentially a photo, and photos are the single biggest contributor to PDF file size.
Embedded High-Res Images
Photos pasted at print resolution (300 DPI or higher) are far larger than what a screen actually needs to display.
Multiple Embedded Fonts
Documents using several custom fonts embed each one fully, adding noticeable weight especially in longer files.
Step-by-Step: Compress a PDF with NexaTools
- Open the NexaTools Compress PDF tool
- Upload the PDF you want to shrink
- Choose a compression level balanced, or maximum compression
- Preview the estimated new file size
- Download your compressed PDF, ready for email or upload
✦ Choosing a Compression Level
Balanced compression keeps images sharp enough for on-screen reading and is the right choice for most emails and online forms. Maximum compression is best reserved for cases where file size is the only priority, such as uploading to a portal with a strict size limit, since it can visibly soften image quality.
How Much Can You Actually Shrink a PDF?
Scanned documents often compress the most sometimes 60-80% smaller since scan resolution is usually far higher than needed for screen viewing. Text-only PDFs from Word or Google Docs are already small and will not shrink much further, since there is little image data to reduce in the first place.
When Compression Is Not the Right Fix
- Legal documents requiring exact reproduction avoid maximum compression on anything with fine print, signatures, or seals
- Print-ready files if the PDF is headed to a professional printer, compress lightly or not at all to preserve image resolution
- Already-small files if your PDF is a few hundred KB, compression will not meaningfully change anything worth doing
Other Ways to Reduce PDF Size Before Compressing
- Scan documents at 150-200 DPI instead of 300+ DPI if the destination is digital, not print
- Remove unnecessary pages using the Split PDF tool before compressing what remains
- Convert color scans to grayscale when color is not necessary for the content
- Avoid embedding unnecessary fonts if you created the PDF from Word directly
✦ Sending Multiple Files?
If you need to send several documents together, compress each one individually first, then use the
Merge PDF tool to combine them into one lightweight file.
🗜️ Compress Your PDF Free
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⚡ Open Compress PDF Tool