pdf91.com exists because the public record on this domain is empty: no meaningful archived snapshots, no company listing, no trace of a service ever operating here. Rather than invent a history, the site documents the one subject the name unambiguously points to — the Portable Document Format — and reads '91' as a reference to 1991, the year the format's founding memo was written.
The material here is compiled from published standards (ISO 32000, ISO 19005, ISO 15930, ISO 24517, ISO 14289) and from documented industry history. Nothing on this site is sold, no services are offered, and no affiliation with any software vendor is claimed or implied.