Email providers cap the size of attachments, and PDFs made from scans or photos easily exceed those caps. A 40-page scanned contract can be 60 MB, while the same contract typed in a word processor is often under 1 MB. The fix is to remove the weight the reader does not need.
Know the limit you are aiming for
| Service | Approximate attachment limit |
|---|---|
| Gmail | 25 MB per message |
| Outlook.com | 20 MB per message |
| Many company mail servers | 10 MB per message |
Because email encodes attachments as text before sending, the file that arrives is about 33% larger than the one on your disk. Aim for 10 MB or less to be safe with almost any recipient.
Step 1: Try lossless compression first
Lossless compression rewrites the internal structure of the PDF, removing duplicate objects and packing the rest more efficiently. Text stays selectable, links keep working, and forms stay fillable. For documents exported from Word, Google Docs, or design tools, this alone often gives a meaningful saving.
Step 2: Re-encode pages only if you must
If the PDF is mostly scanned pages or photos, lossless compression cannot shrink the images inside it. Re-encoding renders each page as a JPEG at a lower resolution. This makes a dramatic difference for scans, but the output pages are images, so text can no longer be selected or searched.
Our Compress PDF tool has a Target size mode that does this automatically: it tries lossless optimization first, then searches for the highest image quality that still fits under the size you enter.
Other ways to make a PDF smaller
- Split it. If one part of the document is huge, split the PDF and send the parts in separate emails.
- Remove pages. Cover sheets, blank scans, and duplicate pages add size without adding value. Delete them.
- Convert to grayscale. Color scans of black-and-white documents waste space. Grayscale PDF often halves their size.
- Share a link instead. For very large files, upload to your own cloud storage and send a link.
Why compress in the browser?
Documents you email are often the sensitive ones: contracts, medical forms, tax records. Most online compressors upload your file to a server to process it. Online PDF Editor runs the compression inside your browser, so the document never leaves your device. See how browser-based PDF tools work for the details.