How to make a PDF small enough to email

Know the limit you are aiming at

Most email services cap attachments somewhere around 20 to 25 MB, and the receiving server can be stricter than the sending one. A file that leaves your outbox can still bounce at the other end.

Aim comfortably under the limit rather than just below it. Attachments are encoded for transport, which adds roughly a third to the size in transit.

What actually makes a PDF heavy

Text takes almost no space. In a large PDF the weight is nearly always pictures.

• Scans: every page is a photograph of paper, often at 300 dots per inch or more.
• Photos placed at full camera resolution, then shrunk on the page — the whole original is still stored.
• Exports from design software, which embed images at print quality.
• Embedded fonts and attachments, which are smaller but add up.

Compress it

1. 1Open Compress PDF and add your file. Up to 15 files, 25 MB each.
2. 2Start at the default, which changes no pixels at all, and see what it saves.
3. 3If that is not enough, try 50%. On most scans and photo-heavy documents this roughly halves the file with no difference you can see at normal size.
4. 4Check the new size against your limit before sending.

Text, fonts, links and page structure are left alone, so the document stays searchable and the text stays sharp at any zoom. If a file cannot be made smaller, you get the original back rather than a bigger one.

If it is still too big

• Remove blank pages. Double-sided scans are usually half empty.
• Convert to greyscale. A grey pixel holds a third of the data of a colour one, and most scans do not need colour.
• Split the document and send it in parts, which also helps the reader.
• For very large files, share a link from cloud storage instead of attaching.

How far is safe

Judge by use, not by number. A contract being read on screen can take heavy compression. A document going to a printer, or one where small print must stay legible, cannot.