PDF, the “Portable Document Format” developed by software giant Adobe, has the PDF/A subtype designed for long-term sustainability. PDF/A is internationally held as the standard for (formatted) text documents. A PDF/A is a stand-alone document: all fonts and images are included in the file, so that it does not depend on other files on the computer to display the content correctly.
PDF/A has a number of subtypes. The PDF/A-1a subtype sets further requirements for the text within the document and is recommended for text documents made entirely with the computer (born-digital). The PDF/A-1b subtype is more suitable for digitized documents.
Many computers will already have software installed with which PDF files can be opened, if not the Adobe Reader can be downloaded for free. Adobe software for creating PDF files is not free, but various free software packages such as OpenOffice and IrfanView also offer PDF support. There are also print programs with which documents can be “printed” to a PDF document, for example the free Bullzip PDF printer.
When text documents are created or converted from non-preferred formats such as Microsoft Word, PDF/A is the preferred format for long-term durability and accessibility.
However, a conversion from regular PDF to PDF/A is undesirable. If an original text document is a regular PDF, a conversion to PDF/A will offer little added value. In addition, such a conversion even offers the possibility of data loss. That is why original PDF documents that are not PDF/A are also accepted by DANS and included as such in the archive. However, DANS cannot guarantee the accessibility and durability of regular PDF documents.