Suffix for many an email attachment

• E-mail file format: Abbr
• Common attached file
• Sharable file format
• Adobe sharable file format: Abbr
• Certain e-mail attachment
• Adobe filename extension
• Difficult-to-change computer file
• Common email attachment type
• E-book format, often

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
by 1992, initialism (acronym) for portable document format , a generic term.