How to reduce a PDF's size to send it by email

You've got everything ready, you go to attach the PDF to your email, and up pops the warning: the file is too big. Almost every email service caps messages at somewhere between 20 and 25 MB, and a single PDF with photos or scans blows past that easily. The good news is that you can nearly always shrink it a lot without any noticeable drop in quality, once you understand what's making it so heavy in the first place.

Why a PDF gets so heavy

Text takes up almost nothing. What sends a PDF's size soaring is almost always the images: photos, high-resolution logos, and above all scanned pages. When you scan a document, each page is saved as a large photograph inside the PDF, even though to you it looks like "just text". Ten scanned pages can weigh more than an entire book of real text.

On top of that, there are other things quietly bloating the file without you seeing them: fully embedded fonts, duplicate copies of the same image, leftover editing data, or thumbnails that some programs add. Reducing a PDF basically comes down to re-compressing those images to a reasonable size and stripping out whatever isn't needed.

How to shrink it without ruining the quality

The trick is to lower the image resolution just enough for whatever you're going to do with the document. You don't need the same quality to print a poster as you do for someone to read a contract on a phone screen.

• If it's for reading on screen or sending by email: you can compress pretty aggressively. The text still looks sharp and the images stay perfectly clear to read.
• If it has to be printed: compress less, so the photos don't come out pixelated on paper.
• If you only need to send a few pages: remove the ones you don't need first. Fewer pages means less weight, especially if they're scanned.

Extra tricks when it's still too heavy

• If you've got several documents, don't cram them all into one giant PDF: send them separately or split the send across two emails.
• Check whether the PDF carries huge images that add nothing (decorative backgrounds, signatures scanned at maximum resolution) and consider removing them.
• If you're going to scan the document yourself, pick a medium quality on the scanner (150–200 dpi is usually plenty for text) instead of the default maximum.

And if, after compressing, the file still won't fit, it's almost always easier to split the document into parts than to wrestle with the quality: dividing it into two lighter PDFs and sending them in separate messages tends to be the quickest, cleanest fix.