When you password protect PDF documents, people who enter the correct password can access the file or folder. A stronger security method is encryption, with common types being 128-bit key or 256-bit AES. Encryption turns PDF content into unreadable cipher text. To decrypt the document, authorized users need a key, which is typically a password or digital certificate.
When you use the Acrobat online tool to password protect a PDF file, it encrypts the document for added security. If you need more advanced PDF security, you can try Adobe Acrobat Pro DC free for seven days to add encryption options, encrypt with certificates, or manage security settings to restrict editing, printing, or copying. Acrobat Pro DC also lets you edit PDFs, organize PDF pages, and convert PDFs to and from Microsoft Office apps – including Microsoft Word documents, PowerPoint presentations, and Excel spreadsheets.