Compare · checked November 4, 2026
How Keepsign compares, with the receipts.
Every app below is good at something. This page only lists what we could verify: our own tests, or each company’s published pages. When we didn’t check something, the cell says so. Prices are US App Store or US website prices on the date shown.
| Keepsign PDF | Preview (Apple) | Adobe Acrobat | PDF Expert | PDFelement | |
|---|---|---|---|---|---|
| Price | Free; Pro US$29.99 once | Included with macOS, and with iOS and iPadOS 26 or later1 | Reader free; mobile premium $48.99–$69.99 a year or $9.99 a week; desktop Pro about $19.99 a month on an annual plan3 | $79.99 a year for all devices, or $139.99 lifetime for Mac only4 | Mac: $79.99 Standard or $119.99 Pro perpetual, or $59.99–$79.99 a year; iPhone: from $6.99 a week or $29.99 a year6 |
| One purchase for iPhone, iPad and Mac | Yes | Built in | No, subscription | NoThe lifetime licence is Mac only | NoMobile and Mac sold separately |
| Fill a field in a signed PDF and save | Signature stays valid, with a receipt | Signature no longer validOur test0 | Not tested | Free version didn’t save without starting a paid trialOur test0 | Not tested |
| Attachment, layer and page labels after that save | Kept, and counted in the receipt | RemovedOur test0 | Not tested | — | Not tested |
| Warns before a save breaks a signature | Yes | No warningOur test0 | Not tested | — | Not tested |
| Digital ID (certificate) signatures | iPhone, iPad and Mac, free | Not in Apple’s guide1 | On the desktop; not in Reader for iPad, per an Adobe employee (June 2025)2 | Not offered; basic signatures only5 | Yes, as a paid add-on ($9.99 a month on Mac)6 |
| Edit existing text | Pro, all devices | Not in Apple’s guide | Paid plans | Paid plans | Not checked |
| PDF to Word | Pro, on device | Not in Apple’s guide | Paid plans | Paid plans | Not checked |
| Compare two versions | Pro, all devices | — | Paid, desktop | Paid, Mac only | Not checked |
| AI assistant | Pro, runs on device, quotes checked | — | Paid add-on ($6.99 on mobile)3 | In paid plans; its privacy notice lists cloud AI providers | Paid add-on ($3.99 a month on Mac)6 |
| Shortcuts and Spotlight | 19 Shortcuts actions; Spotlight by content | — | Not mentioned on its App Store page | Not mentioned on its App Store page | Shown on its Mac App Store screenshots6 |
| Account needed | No | No | Not checked | Some reviews report a required login | Not checked |
“—” means it doesn’t apply or the company doesn’t list it. “Not tested” and “Not checked” mean we didn’t verify it, not that the app can’t do it.
Fair is fair.
Preview is already on your Mac and, since iOS 26, on your iPhone. For reading, quick notes and signing a PDF nobody signed before, it may be all you need.
Acrobat is the reference for heavy office work on Windows and Mac, prepress, and sending documents out for signature with tracking, which Keepsign doesn’t do. PDF Expert is a polished Mac and iPad app with a long track record. PDFelement has a broad toolset on Mac and Windows.
Keepsign is for when signatures and the integrity of the file matter, when you want the same app on all three Apple devices, and when you’d rather pay once and keep your files on your device.
The signed-PDF test
On November 4, 2026, on macOS 26.5.2, we made one test PDF with a real CMS signature, a script that runs on opening, an attachment, an optional layer, page labels, a language tag, accessibility tags, XMP metadata and a sticky note. In each app we changed one form field from “Ana Pérez” to “Luis Prueba” and saved the way the app allows. Then we checked the signature with OpenSSL against the bytes it covers, and unpacked the file to look for each piece.
- Preview (macOS 26.5.2): saved over the original by rewriting the whole file. The field changed, the signature no longer matched, and the script, attachment, layer and page labels were gone. No warning.
- PDF Expert 3.13.5, free: pressing Save offered a 7-day paid trial; without starting it, nothing was written.
- We also tested PDFgear 2.29, which saved a copy and removed the signature, and UPDF 2.5.7 free, which kept the signature valid but added its logo to page 1 when saving.
We didn’t test paid versions, the iPhone and iPad versions of these apps, or how Acrobat reports the results. The verdict is the byte-level check, not a full PAdES validation.
Sources
- Keepsign test of November 4, 2026, described above.
- Apple, Preview User Guide for Mac (support.apple.com/guide/preview) and Get started with Preview on iPhone (support.apple.com/guide/iphone), read November 4, 2026.
- Adobe Community, answer by an Adobe employee on certificate signatures in Acrobat Reader for iPhone and iPad, June 2025.
- Acrobat Reader App Store listing (id 469337564), in-app purchases, November 4, 2026; desktop prices from xodo.com/blog/adobe-acrobat-pricing-explained, as adobe.com wasn’t reachable for us that day.
- pdfexpert.com/pricing, November 4, 2026. It also says “Additional new features may come at an extra cost.”
- Readdle support, “Sign PDF documents” (support.readdle.com/pdfexpert).
- PDFelement Mac App Store listing (id 1470732135) and PDFelement iPhone listing (id 1516765045): in-app purchases and screenshots, November 4, 2026.
Adobe, Acrobat, PDF Expert, Readdle, PDFelement, Wondershare, PDFgear and UPDF are trademarks of their owners. This page isn’t affiliated with or endorsed by them. Found something out of date? Write to support@keepsignpdf.com and we’ll fix it.
Get one email when Keepsign is out
One message on launch day, then we delete your address. No newsletter. How we handle it.