First, decide which kind of app you need
"Electronic signature app" covers two different products. Sending platforms — DocuSign, Adobe Acrobat Sign, Signeasy — let you send documents to others and track signatures. Signing apps let you sign a PDF you already have.
If you send, stop here and compare sending platforms. If someone emailed you a PDF and you need to sign it and send it back, the checklist below is for you. For head-to-head picks, see the best PDF signing app for iPhone, by job.
Signers and senders value different things. A sender cares about reminders, audit records and team seats. A signer cares about getting one file signed correctly and sent back without creating an account. Most app roundups rank on the sender's list, which is why they rarely help someone holding a lease in Mail.
Five things to check before you pay
- ✓Flattened export. The signature should become part of the page, not a layer on top. Otherwise people on Windows or Android may see a blank line.
- ✓No account. You shouldn't have to create a login to sign one PDF.
- ✓On-device processing. Leases, W-9s and offer letters carry personal data. The file shouldn't need to leave your iPhone.
- ✓Real form fields. Dates, initials, checkboxes and text — not just a drawn signature you drag around.
- ✓A pricing model that fits. If you sign a few documents a year, a monthly plan or an envelope count is the wrong shape.
How the common options stack up
Against the five checks, for someone who signs PDFs they received.
| Feature | Apple Markup | Adobe Fill & Sign | DocuSign | eSign PDF |
|---|---|---|---|---|
| Flattened export | No, annotation | Depends how you save | Completed file from service | Yes, every export |
| No account | Yes | For basics | Account to send | Yes |
| On-device | Yes | Device or Adobe cloud | Cloud | Yes |
| Dates, checkboxes, initials | Text boxes only | Yes | Sender places fields | Yes |
| Pricing model | Free | Free basics, paid upgrades | $11/month billed annually (Personal) | $59.99 once |
| Sends for others | No | No | Yes | No |
DocuSign pricing checked 2026-09-26. Other eSign PDF plans and local prices are shown in the App Store.
Why flattening matters more than features
The most common failure isn't a missing feature. It's a signature that looks fine on your iPhone and is missing on the other person's screen. Apple's own community forum has threads about Markup edits not showing on non-Apple devices, and PDF users on forums recommend flattening so signatures show in Acrobat.
Any app you pick should either flatten automatically or make it obvious how. This is also the fix when you can't sign a PDF on iPhone the way the recipient expects.
Red flags when you only need to sign
- ✕A sign-up screen before you can open your PDF.
- ✕A paywall that appears halfway through signing, after you've placed every field.
- ✕A weekly plan for something you do a few times a year.
- ✕No way to tell whether the export is flattened.
- ✕Uploading your document to a website or cloud service just to add a signature.
- ✕An envelope or document limit on signing your own files.
Short picks by situation
Permission slip to a teacher on an iPad: Apple Markup. Free.
Twelve-page lease with initials on every page: eSign PDF. Fields, flattened export, $59.99 once.
You want free and already use Acrobat: Adobe Fill & Sign.
You send contracts to clients: DocuSign or another sending platform.
You're on Android: not eSign PDF — it's iPhone and iPad only.
Verdict
Choose a sending platform if you send
DocuSign is well rated and does it well. DocuSign Personal: $11/month billed annually ($132/year), 5 envelopes/month.
Choose Apple Markup if it's simple
One signature, Apple recipient, no cost.
Choose eSign PDF if you sign what you receive
Flattened, no account, on-device, real fields, $59.99 one-time (US).
FAQ
What should I look for in an iPhone signature app?+
Flattened export, no account, on-device processing, date and checkbox fields, and a price model that fits how often you sign.
Is an electronic signature made on iPhone valid?+
In the US, the ESIGN Act says a signature can't be denied legal effect just because it's electronic. Some documents have their own rules, and a sender may require a specific platform.
Do I need a subscription to sign PDFs on iPhone?+
No. Apple Markup is free, and eSign PDF is $59.99 one-time (US). Other plans and local prices are shown in the App Store.
Is Apple Markup good enough?+
For one signature going to someone on an iPhone or Mac, yes. For long forms, dates and checkboxes, or recipients on Windows and Android, use an app that flattens the file.
Which app should I use to send a document for someone else to sign?+
A sending platform such as DocuSign. eSign PDF does not send documents for signature.
Sources
- Apple iPhone User Guide: Fill out forms, sign documents, and create signatures
- Apple Community: Markup edits not showing on non-Apple devices
- MacRumors Forums: flattening PDFs so signatures show in Acrobat
- 15 U.S.C. § 7001 — Electronic Signatures in Global and National Commerce Act (ESIGN)
- DocuSign eSignature plans and pricing