PDF Too Large to Email? Get Under 25MB

Aim for 18MB or less if you are sending through Gmail, even though the cap is advertised as 25MB. Email attachments are base64-encoded on the way out, which makes them roughly a third bigger, and the cap applies to the encoded message. A 25MB PDF therefore fails while a PDF of about 18MB goes through. We measured this in our [video email guide](/blog/compress-video-for-email): an 18,000,000-byte attachment became a 24.3MB message. Outlook.com is stricter at 20MB, so the safe target there is closer to 14MB. Check the limit on the receiving side too, because a company mail server can reject a file your own provider accepted.

A PDF is large because of its images, almost never its text. A 40-page report made of typed text is usually a few hundred kilobytes, while the same report built from phone scans or exported slides with full-resolution photos can pass 30MB. That decides your fix. If the file is mostly photos or scans, compression will work well. If it is mostly text and vector graphics, compression will barely move it, and splitting is the better route. Open the file and try selecting a sentence: if you cannot, every page is a picture and the images are your target.

Open the [Compress PDF tool](/compress-pdf), choose a quality and check the size it reports. It runs in your browser, so a contract or ID scan is never uploaded. In the source, the three levels re-save embedded images as JPEG at quality 0.4, 0.6 and 0.75, and shrink anything wider or taller than 1,200, 1,600 or 2,000 pixels. Start with medium. Low is the one to reach for when you are 5MB over the line and the file is only being read on screen. High keeps small print crisp but saves the least.

If the size drops by only a few percent, the file has little to give. The tool only keeps a recompressed image when it is at least 10 percent smaller than the original, so images that were already efficient are left alone, and text-only PDFs have no images to touch. Do not keep re-running it: a second pass over the same images only adds blur. Our guide on [why compressed PDFs stay huge](/blog/compressed-pdf-still-huge) covers the cases where the bulk is fonts, scans stored as non-JPEG images or embedded attachments. At that point, split the file instead.

A split always works because it adds no quality loss. Use the [Split PDF tool](/split-pdf) to cut the document at a sensible page, for example the end of a chapter, then send the parts in separate messages and number the subjects "1 of 2" and "2 of 2". The pages are copied across unchanged, so each part is about half the original size. Aim for parts well under 18MB, and if one part is still over, split that part again. Our [guide to splitting PDF files](/blog/how-to-split-pdf-files) covers page ranges and extracting single pages.

If the PDF must stay whole and uncompressed, such as a print-ready brochure, attach nothing. Upload it to a cloud drive and send the link. Gmail does this automatically for large attachments through Google Drive, and Outlook has OneDrive. The trade-off is that the recipient needs access, and the link can outlive the conversation, so set an expiry and avoid link-sharing for sensitive documents. For anything private, shrinking or splitting locally and attaching the result is the safer choice.