Email attachment, often

• Difficult-to-change computer file
• Format for an e-ticket
• Digital doc format
• Suffix for many a sharable computer file
• Graphical file format
• E-mail file format: Abbr
• File that might be e-signed
• Printable crossword, perhaps

Wikipedia Word definitions in Wikipedia
PDF is the Portable Document Format in computing. PDF or PdF may also refer to: