On Windows I cannot place an electronic signature. What should I do? How do I digitally sign a document with Acrobat Reader DC? The validity of my signature is unknown. What should I do? My digital signature is invalid. What should I do? On Mac I cannot place an electronic signature. What should I do? My digital signature is invalid. What should I do? The validity of my signature is unknown. What should I do? How do I set a digital signature with Acrobat Reader DC? How do I digitally sign a document with Acrobat Reader DC? On Linux How do I electronically sign a document in Acrobat Reader DC? How can I configure Libreoffice to sign documents with the eID? How can I sign documents with Libreoffice? How can I sign existing PDF files in Libreoffice? How can I sign PDF files with a timestamp in Libreoffice?
