Can't sign a PDF on iPhone?

The Markup button is missing

You opened the PDF but there's no pen icon. That usually means you're in a quick preview, not an editor. Gmail, Outlook, Slack, and some bank apps show PDFs in their own viewer, and Messages can open a preview with fewer options.

Fix: tap the Share button and choose Save to Files. Open the PDF from the Files app and the Markup icon appears. Or choose Markup directly from the Share Sheet if it's listed. Apple's iPhone guide on filling out forms and signing documents walks through the Markup side.

Signing an emailed PDF? The reply steps are in sign a PDF from an email and send it back. Is Apple's free tool the cause? Compare in Apple Markup vs a signing app.

The PDF is locked or password-protected

Some PDFs ask for a password to open. Others open fine but block editing, commenting, or form filling. The owner set those restrictions, often a bank or HR system protecting a statement or contract.

There's no honest workaround. You need the password or an unlocked copy. Reply to the sender and ask for a version you can sign. Or ask whether they have a signing link instead. The eSign PDF app can't sign a protected PDF without the owner's password either. Also, be wary of any website that promises to strip the protection for you.

You signed it, but they can't see it

This is the most common one. On your iPhone the signature looks fine. The other person opens it on Windows or Android, and the line is blank. Or the signature looks like a loose drawing in the wrong place.

Markup adds your signature as an annotation, a layer on top of the page. Apple apps show it; some other viewers and document systems don't. There's an Apple Community thread about exactly this: Markup edits not showing on non-Apple devices.

Fix: flatten the PDF so the signature becomes part of the page. Markup doesn't have a flatten button, which is where a signing app helps. More in Apple Markup vs a signing app.

Mail sent the original, not the signed copy

You signed in Markup, then went back to the email and hit Reply, and the attachment was the unsigned file. Or you saved the signed PDF to Files but attached the old one from your downloads.

Fix: after marking up an attachment in Mail, tap Done and use the reply Mail creates with your marked-up file. If you signed in Files, start a new reply and attach the file from Files by name. Open the attachment in your Sent folder to confirm it's the signed one.

The file is too big to send

Scanned documents and photo-heavy PDFs can be large. Many email providers limit attachments to around 20–25 MB, so the message bounces or never arrives.

Fix: in Mail, accept the Mail Drop option when it appears for a large attachment, which sends a download link instead. Or share the file with AirDrop or a Files link. If you scanned it yourself, rescan with fewer pages or lower quality.

Still stuck? Sign it with eSign PDF