When someone emails documents to you, you can sign them on your iPhone or iPad via the Markup preview in the built-in Mail app. You can sign PDFs or other types of documents sent as attachments. Here’s how:
Preview the attachment in the Mail app.
Tap the toolbox icon, and then tap the Signature button in the Markup preview.
Sign the document using your finger on the touchscreen, and then tap Done.
Place the signature where it belongs in the document, and then tap Done again.
When you reply to the sender’s email using the Mail app, the sender receives your signed attachment.
(This how-to is based on my experiences and info on Apple’s support pages — where the images sometimes come from.)
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