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PDF - Wikipedia
History of PDF - Wikipedia
Adobe’s PDF Format Adopted as Standard - WIRED
30 years of PDF: The file format that changed the world
PDF Specification Archive - PDF Association
PDF/X and the other PDF standards – PDF Association
PDF Evolution: ISO Standards, Subsets, Versions and Types
ISO 32000-1:2008(en), Document management ? Portable …
History of the Portable Document Format (PDF) | Encyclopedia MDPI
ISO 32000-1:2008 - Document management — Portable …