PDF Specification

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The widely used document format known as the "Portable Document Format" (PDF), was standardized as ISO 32000. It is a file format developed by Adobe starting in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating systems. Based on the PostScript page description language, each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, vector graphics, raster images and other information needed to display it.

PDF was standardized as ISO 32000 in 2008 and is based on the Adobe PDF 1.7 specification document. This specification document can be viewed and downloaded here. PDF files that are created with compliance to earlier versions of the specification, e.g. compliance with the 1.5 specification, correspond to the Adobe Reader version 1+n, so 1.5 compliance would equate to the Adobe Reader version 6. Legacy copies of the Adobe specifications 1.2 to 1.7 can be found on Adobe's website.

The current edition as ISO 32000-2:2020 was published in December 2020, but an update is in progress (ISO 32000-2:2020/CD AMD 1). Copies of the latest versions of the specification, which runs to almost 1000 pages, can be purchased from the International Standards Organization:PDF2.0-ISO

PDF files may contain a variety of content besides flat text and graphics including logical structuring elements, interactive elements such as annotations and form-fields, layers, rich media (including video content), three-dimensional objects using U3D or PRC, and various other data formats. The PDF specification also provides for encryption and digital signatures, file attachments, and metadata to enable workflows requiring these features. The new PDF 2.0 (ISO 32000-2) standard will deprecate (note A, below) a number of features of earlier PDF standards, including the use of any encryption algorithm weaker than AES256, and removal of sound and video annotations.

note A: 'Deprecated' means that a feature should not be used when creating new PDF 2.0 documents. However, it may still be supported in viewers for processing existing documents or even PDF 2.0 document which still contain deprecated features.