Serial document signing (PAdES)
Visual seals
PAdES supports visual seals as a visual representation of a digital signature.
The merchants may decide whether or not visual seals should be included with the signatures. By default visual seals are added to the document.
When inserting visual seals, the visual seal size is adjusted according to the document DPI.
The merchants may also decide where to place the visual seals using x and y coordinates of the document and by providing the page on which the seal should be placed. The ClientProxy validates these parameters:
- If the page number is out of range, the seal is placed on the first page of the document
- If the x or y coordinates are out of bounds, the seal will be placed below/left of existing signatures, or default to the upper left corner of the page.
Visual seal positioning recommendations
We recommend placing visual seals so that they do not overlap with text or graphics.
Based on experience from user tests visual seals should be placed at the bottom of a page. Users tend to look for signature fields at the bottom of a page.
Digital signature support in PDF readers
PDF readers support for visual seals varies. The following compatibility matrix are based on the latest PDF reader versions (as of 4th December 2018).
Reader name | Platform | Visual seal | Signature inspection | * |
---|---|---|---|---|
Adobe Acrobat | Desktop* | Yes | Yes | Tested with same results on:
|
Apple preview | macOS | Yes* | No | *The signature (visual seal), as well as text elsewhere in the document, may be slight malformed. * Signatures may appear skewed and/or out of place, when compared to viewing it in acrobat on desktop. Looks similar as in iBooks (see screenshot in test notes on iBooks) NOTE: The issue of malformed visual seal was present during the first few weeks of testing, but was later found not to be an issue anymore. It is not known what changed in the meanwhile. Tested on:
|
Foxit reader | Desktop, Android | Yes | Inspection on Windows only, not on MacOS | Tested on:
|
Foxit Phantom | Windows | Yes | Yes | |
Foxit Phantom Standard | MacOS | Yes | Yes* | *Does not support displaying long names in PDF signature metadata (name cropped for user 25064310510) |
Foxit business (= Foxit MobilePDF business) | iOS, Android | Yes* | Yes* | *Claims it can inspect. Not verified. Behind paywall |
Foxit mobilePDF | iOS, Android | Yes | Yes* | iOS: Limited functionality. Must validate with trusted certificates. Android: No inspection |
Evince* | Desktop (*Windows desktop only) | Yes* | No | *Visual seal present, but looks grainy. Text may be malformed. (tested on Win7/Evince 2.32.0.145) |
Google Chrome | Desktop | Yes | No | Tested with same results on:
|
Firefox | Desktop*, iOS** | No | No | * Tested w/ MacOS High Sierra, Firefox Quantum 62.0 **Tested w/ iPad Air 2 (iOS 10.3.2) and iPhone 8+ (iOS 11.2.6) |
Google Chrome | iOS | No / Yes* | No | iPad Air 2 (iOS 10.3.2): Visual seal not present when viewed in Chrome (both in version 56.0.2924.79 and version 69.0.3497.91). iPhone 8+ (iOS 11.2.6): Visual seal is not present/displayed OK when viewed in Chrome directly from download (opening in new window). *Visual seal is present when viewed in Chrome on devices with iOS 12:
|
iBooks | iOS | Yes* | No | * Signatures may appear skewed or out of place, when compared to viewing it in acrobat on desktop.
|
Adobe Acrobat | iOS, Android | Yes* Yes | NO | *In Adobe Reader on Android mobile devices, a top menu covers the uppermost part of the first page of the document. If the visual seal is placed in the default (top left) position, the user will need to tap the document to activate viewing the document without top menu in order to see the visual seal. On phones it will be completely covered on first sight (before/unless tapping the document). On tablets it will be partially covered by the menu. |
Google drive* | Android | Yes | No | Tested on:
|
Edge | Desktop Windows 10 | Yes | No |
Based on the above matrix it is apparent that the regular user may be unable to view and/or inspect the visual signatures unless 3rd party software is installed on their devices.