PDF versions

The PDF specification has gone through multiple versions since its first version was published in 1993. Each release has added new features. All non-deprecated features in a PDF version are also included in subsequent versions. A PDF file includes a header identifying the PDF version to which it conforms. A PDF reader will attempt to read any PDF file, even if the file’s version is more recent than the version that the reader implements.

Table 1. PDF specification versions

VersionYearAcrobat Reader version

There are also specialized subsets of PDF that have been standardized by ISO. Some of these have multiple versions that are each based on a specific PDF version.[5]

[5] AH Formatter does not generate either PDF/E or PDF/VT.