Configurable PDF permissions checker to prevent or force signing documents that disallow it
This is disabled by default due to ETSI standard and ISO 32000-2 allowing to sign protected documents, but this would be useful to support because end users will see invaid signature errors on Acrobat, which aligns to ISO 32000-1 document restrictions, but not tested if this is based on PDF version of the document somehow:
https://ec.europa.eu/digital-building-blocks/DSS/webapp-demo/doc/dss-documentation.html#ProtectedPDF
A checkbox for turning of this restriction in Settings would be useful. Considering this as a sane but toggleable default for legacy PDF compatibility and because lots of users still use the Adobe validator, despite the BCCR validator shows them as valid, in Adobe will fail when a protected PDF has signatures after being protected.