Feature Request: Flatten everything

[robinduerhager]

Hey,

i just noticed, that only Formfields will get flattened into the pdf, however i have the use case for also flattening annotations made with a pen on a tablet into the pdf file. Sejda.com actually has the feature (so i guess sejda SDK provides the functionality for this?) to flatten everything, but i thought this would be great for PDFSam aswell, since it already can flatten Forms.