How to Sign a PDF on iPhone — 3 Free Methods (2026)

Someone sends you a PDF to sign. You're on your iPhone. You could print it, sign it, scan it back — or you could sign it on your phone in under a minute and send it straight back. Here are the three best free methods. (On a computer instead? See our guide to signing a PDF free.)

Method 1: PrimeDocu in Safari — Best overall (free, encrypted, saves signed documents)

PrimeDocu's PDF signer works in any mobile browser — no download required. Your signed documents are stored with AES-256-GCM encryption and the free plan has unlimited signatures with no watermark.

1. Open Safari on your iPhone and go to primedocu.com. Create a free account (no credit card).
2. Upload the PDF — tap to select from Files, Mail, or any other app.
3. Tap "Sign" in the document toolbar.
4. Draw your signature with your finger on the touchscreen, or type your name in a cursive font, or upload a saved signature image.
5. Drag the signature to the correct position on the page. Resize it by pinching.
6. Add anything else needed — text boxes for printed name, date field, initials.
7. Download or share — save the signed PDF to Files, email it directly, or copy a share link.

Best for: regular use, when you want signed documents stored securely and accessible across all devices.
Free tier: unlimited signatures, no watermarks, 1 GB encrypted storage.

Method 2: Apple Markup — Best for a quick one-off signature (no account needed)

iOS has a built-in PDF annotation tool called Markup. It's fast, requires no account, and works completely offline. The signed PDF saves back to wherever the original was (Files, Mail attachment, etc.).

1. Open the PDF in the Files app, or tap and hold a PDF attachment in Mail and choose "Markup".
2. Tap the pen icon (bottom right) to open the Markup toolbar.
3. Tap the + button at the far right of the toolbar and choose "Signature".
4. Draw your signature with your finger or Apple Pencil. Tap Done.
5. Drag and resize the signature to position it on the page.
6. Tap Done (top right) to save. The PDF is saved back in place automatically.

Best for: quick one-off signatures with zero setup.
Limitation: no cloud storage, no saving for reuse across apps, iOS only.

Method 3: Adobe Fill & Sign — Best for filling form fields and signing

Adobe's free iOS app handles both form filling and signature placement, making it a good choice when a PDF has fields to complete (name, address, date) as well as a signature line.

1. Download Adobe Fill & Sign from the App Store (free).
2. Open the app and import your PDF from Files, email, or other apps.
3. Fill in form fields — tap any field to type text. Adobe auto-detects field positions.
4. Tap the signature pen icon in the toolbar to add your signature.
5. Draw or type your signature, then tap to place it on the signature line.
6. Share or save the completed PDF.

Best for: forms that need both filled fields and a signature.
Limitation: requires an account for some features; Adobe cloud storage (not encrypted).

Comparison: signing a PDF on iPhone

Method	Download needed	Account needed	Encrypted storage	Saves signature
PrimeDocu	❌ Browser only	Free account	✅ AES-256-GCM	✅
Apple Markup	❌ Built into iOS	❌ None	❌	✅ (per app)
Adobe Fill & Sign	✅ App required	Free account	❌	✅

Frequently asked questions