PDF (Portable Document Format) is a file format developed to display documents (including text and images). It is designed to be software, hardware, and operating system independent. There are several ISO standards that cover PDF:
Standard file format
Developed by Adobe as a proprietary format (Adobe PDF 1.0) in 1992, PDF was designed to be a digital form for representing electronic documents. The format enable users to exchange and view electronic documents independent of the environment in which they were created or the environment in which they are viewed or printed.
PDF files may contain a variety of content:
- flat text
- graphics (images)
- logical structuring elements such as document outlines (table of contents)
- interactive elements such as annotations and form fields
- rich media, including video content
- three-dimensional objects using U3D or PRC
- other data formats
The PDF specification also provides for encryption and digital signatures, file attachments, and metadata to enable workflows requiring these features.
PDF 1.7 (ISO 32000-1)
To further increase acceptance of PDF as a format, Adobe Systems submitted PDF Version 1.7 to the ISO for standardization. On July 1, 2008 ISO 32000-1 Document management — Portable document format - Part 1 was published, turning PDF into an ISO standard.
The standard governs the software that creates the PDF files (confirming writers), software that reads PDF files and interprets the contents for display and interaction (conforming readers), and PDF products that read and write PDF files (conforming products).
PDF 2.0 (ISO 32000-2)
Part 2 of the standard was put forward and approved by the ISO members. The list of changes contains more than 50 entries that refer to new features, improvements, and the clean-up of legacy issues that were present in the ISO 3200-1 standard. The new part of the standard mainly concerns rendering, transparency, digital signatures, metadata, and accessibility.
While this new part based on the preceding part, ISO 3200-1 continues to be current. However, the term conforming reader has been replaced and redefined as interactive PDF processor (software that reads and displays PDF content and interacts with the computer users to possibly modify and save the PDF file), PDF reader (software that reads existing PDF files and interprets their contents for display), and PDF writer (software that creates PDF files).
There are several technical specifications that determine the use of the PDF file format within specific applications:
PDF/A – Archive
The PDF/A standard (ISO 19005) defines the specifications for the archiving of digital documents. The PDF/A standard ensures that the visual appearance of electronic documents is preserved over time. This guarantees the readability of PDF/A-compliant documents. There are four versions of this standard.
PDF/X – Exchange
PDF/X (ISO 15930) standardizes PDF as graphics files for printing. Several improvements and changes have been incorporated since it was first drafted in 2001. The current version is PDF/X-5.
PDF/UA – Universal Accessibility
PDF/UA (ISO 14289) aims to make PDF documents accessible to people with disabilities. The standard includes guidelines on how PDF documents and the information elements they contain, such as graphics, text, multimedia elements, and form fields, must be made available so that they can navigate in the document, as well as receive the content via voice output.
PDF/VT – Variable and transactional printing
Printing, packing, and franking transactional documents, whether they are essential business documents such as delivery notices, invoices and payment reminders or direct marketing letters sent out in sheer endless numbers, is a billion dollar market. The high numbers of print jobs and the requirements for short through-put times have not only led to the development of corresponding hardware like high-performance printers. Applications like Variable Data Printing (VDP) have been created in order to significantly cut the cost per printed item. These facts and the huge demand for a universal and standardized VDP solution have led to the development of PDF/VT.
PDF/E – Engineering
PDF/E is a standard for technical documents in engineering, architecture and geo-information. The depiction of 3D objects and the exchange of plans/drawings shall be covered by the PDF/A-4e standard in the future.
PDF/H – Healthcare
PDF/H is a guideline to regulate the creation, exchange, retention, and protection of healthcare-relevant information. PDF/H aims to close the gap between healthcare institutions and the consumer.