"Sign different formats" refers to the fact that digital signatures can be applied to different file formats, with PDF (Portable Document Format) being a commonly used example. Digital signatures can be applied not only to PDF files, but also to a variety of other file formats such as Word documents (DOCX), Excel spreadsheets (XLSX), text files (TXT), images (JPEG, PNG) and more. The way in which digital signatures are applied to different file formats can vary depending on the software and standards.
