How to sign a PDF on an iPhone

Why use Safari instead of the Files markup tool?

iOS does include a built-in Markup feature accessible from the Files app and from email attachments, but it is designed primarily for annotation, not for signing documents the way a dedicated tool is. Markup saves your signature as a basic drawing annotation — a floating overlay that is not permanently flattened into the document unless you explicitly export it correctly. In some applications and on some devices, an annotation-based signature can appear missing or be editable by the recipient.

Markup also stores only a single saved signature (drawn with a finger or Apple Pencil), so you cannot switch between a drawn signature and a typed one, and you cannot upload a high-quality image of your actual handwritten signature. There is no typed-font option, and resizing and positioning is less precise than in a dedicated signer.

A dedicated browser signer gives you all three signature styles, precise placement and sizing controls, and a flattened output PDF — without leaving Safari and without installing anything extra.

Signing an emailed PDF on your iPhone

If the PDF arrived as an email attachment in Mail, tap and hold the attachment, then choose Share to open the iOS share sheet — or save it to Files first. Either way, you can then open the DocSignHub signer in Safari and pick the file from the Files location in the upload dialog.

After signing, download the file and it lands in your Downloads folder inside Files. Use the iOS share sheet to attach the signed PDF directly to an email reply, send it via Messages, or upload it to a cloud service — the whole round trip happens on your phone.

Accessing PDFs from iCloud Drive, Dropbox, or Google Drive

The iOS file picker in Safari shows all storage locations registered as file providers on your phone, including iCloud Drive, Dropbox, and Google Drive if those apps are installed. You do not need to download the file to local storage first — pick it directly from the cloud location in the upload dialog and it loads into the signer.

After signing and downloading, the signed file lands in your Downloads folder in Files. From there you can move it to iCloud Drive or share it back to Dropbox or Drive using the share sheet.

Your document never leaves your phone

Because the signer processes the PDF locally in Safari using WebAssembly, your document is not uploaded to any server. That matters on mobile, where you are often signing something personal — a lease, a medical form, an offer letter — sometimes over a cellular connection with an unknown network. Nothing is transmitted, stored, or exposed to any third party.

This is meaningfully different from cloud-based signing apps, even free ones, which require you to upload your document to their servers before you can sign it. The browser-local approach eliminates that exposure entirely.

Drawing a good signature on a small screen

Signing with a finger on a small phone screen can produce a cramped or shaky result. A few techniques help: sign slowly and use larger, more deliberate strokes than you would with a pen on paper. The signer lets you resize the signature down after placing it, so drawing it slightly larger in the signature pad gives you more control and hides small wobbles when it is scaled to fit the line.

If you have an iPad and a compatible Apple Pencil, signing there and then sharing the result to your phone is an option for the most natural-looking signature. Alternatively, switching to the "type" method on a small phone screen gives a clean, consistent result every time without any drawing at all.

Troubleshooting: PDF does not open or upload

If tapping a PDF link in Safari triggers a download rather than opening the upload dialog, save the file to Files first using the share sheet, then open the DocSignHub signer and pick it from there. Some servers send PDFs with headers that cause Safari to download rather than display them.

If the file picker does not show your expected location, check that the relevant storage app (Dropbox, OneDrive, etc.) is installed and that you are signed in — iOS only shows file providers for apps that are installed and authorized.

• >PDF downloaded instead of opening: save to Files first, then upload from there.
• >iCloud location not showing: open the Files app once to ensure iCloud Drive is activated.
• >File too large: very large PDFs (over 50 MB with many high-resolution images) may be slow to process on older devices.
• >Signature looks blurry: draw larger in the signature pad and scale it down on the page.

Works on iPad too

The same browser-based signer works on any iPad in Safari, Chrome, or any other modern mobile browser. On an iPad with Apple Pencil, drawing a signature is especially precise and fluid — you get the same natural feel as signing on paper. The larger screen also makes it easier to position a signature accurately, particularly on dense, form-heavy documents.