PDF won't attach to an email: causes and fixes

The email is written and the address is checked, but the attachment won't stick: the mail client spins on upload, complains about size, or silently drops the file. Nine times out of ten the problem is file weight, though a couple of less obvious causes exist too. Let's go through them in order.

The file is over the mail limit

Popular mail services cap a message at around 25 MB, and corporate servers are often stricter: 10 or 5 MB. A fifty-page contract scan blows past those numbers easily. One important detail: the limit counts all attachments in the message combined.

What to do: shrink the document with compress PDF and check the resulting size. Scans built from images shrink several times over. For typical mail limits there is a separate guide: compress PDF for email.

Compression didn't help: the file is still huge

A thick scan running to hundreds of pages may not fit the limit even after compression. Squeezing it until it turns unreadable is a bad idea: the recipient will ask you to resend it.

What to do: break the document into parts with split PDF and send two or three emails with clear numbering in the subject line. Or upload the file to cloud storage and send a link, if the recipient has no policy against links.

Many documents, and some get lost

Five separate attachments are five chances to forget or lose something in transit. The recipient opens three and never gets to the rest.

What to do: gather the documents into one file with merge PDF, in the order they will be read. A single attachment arrives whole or not at all, with no states in between.

The email contains personal data

A passport, a contract, or medical records sent in the open are poor cargo for regular email: the message can be forwarded, and a mailbox can be hacked.

What to do: set a password with protect PDF and pass it to the recipient through another channel: a phone call or a messenger. The file in the email stays closed to anyone without the password.

The attachment arrives corrupted

You sent a healthy file, yet the recipient can't open it. The usual culprit is an interrupted download or an antivirus that cut into the attachment on the way.

What to do: ask the recipient to download the attachment again. If that fails, check your original: open it locally, and try fixing the damaged copy with repair PDF.

Checklist before sending

• Total attachment size is under the mail limit.
• Several documents are combined into one file.
• The file opens locally on your machine without errors.
• Documents with personal data carry a password.
• The password went to the recipient through a separate channel.

Start with the size: compression solves most email problems with PDFs. The rest comes down to care: one file instead of a scatter, a password on sensitive documents, and a quick check before you hit Send.