1. PDF/A - an ISO standard
2. How does PDF/A differ from “normal” PDF?
3. Using PDF/A in practice
4. The aims of the PDF/A-Standard
5. The key rules for PDF/A are as follows

It is becoming increasingly more common for important documents to be saved in PDF format, thus establishing an ever-increasing trend. But will we still be able to open these PDF files without any problem in another ten years’ time? Not to mention, will they still be displayed in the same layout as they have today?

PDF is being enhanced all the time, with new powerful functions being added. All this can present a real challenge when it comes to long-term archiving. Archiving experts and software developers from all around the world have been working since 2002, within ISO and based on Adobe’s PDF specification, on developing standards for 100% archivable PDF files. The outcome of this process was ISO standard ISO 19005-1:2005 
published in October 2005, better known as PDF/A-1.

Anyone choosing to comply with this standard when archiving electronic documents will avoid the ever-present risk associated with most document formats that important information will no longer be accessible in five, ten or even more years.

Based on PDF-Version 1.4 (corresponding to Acrobat 5), the PDF/A standard includes a number of minimum requirements and restrictions (see box), ensuring that PDF documents are always reproduced in a unambiguous manner. The PDF/A standard also has two conformance levels: PDF/A-1a and PDF/A-1b.

PDF/A-1b addresses the integrity of the visual display, whilst PDF/A-1a on top of that requires the content of a PDF document to be marked up (“tagged PDF”) so that its logical structure is still recognizable. It also requires sufficient character set information so that the entire text can be interpreted as Unicode, which is an important basis to be able to search through or extract text.

There are two questions in particular that crop up when people actually come to use this format:

• How can I check whether a PDF file complies with the PDF/A standard?
• How do I convert an existing PDF file to an ISO-compliant PDF/A file?
  

There are a number of PDF/A tools available on the market. The most widely used among these will be Adobe Acrobat Professional 8. The integrated verification function known as Preflight – developed by callas software GmbH and licensed to Adobe – validates all the relevant aspects of the PDF/A standard. Acrobat can even be used to save PDF files in PDF/A format.

callas software has also developed pdfaPilot, a specialized tool offering extensive correction functions that is very easy to use, even though it is extremely powerful.

• Preserving and maintaining an unambiguous way of representing documents
• Ensuring the file is complete, with all the components required to display and reproduce the content
• Prohibiting the use of non-PDF components
• Avoiding dependence on a particular operating system, product or manufacturer
• Only for PDF/A-1a: preserving the logical structure and semantic meaning (particularly of the text)

• Dynamic objects are not permitted
• No external references or dependencies
• No embedded files (e.g. Word files)
• No embedded audio or video files
• Fonts must always be embedded and contain all the letters (glyphs) used
• Any color must be clearly specified
• Forms, comments and notes are only permitted to a limited extent, and must behave in the same way when viewed on screen and printed
• Compression: no LZW or JPEG2000
• No transparent objects
• Features that are not defined in PDF 1.4 must 
not be used (e. g. layers, 3D models)
• No proprietary PDF extensions
• Metadata must be coherent in itself
• PDF/A identifier must be included in metadata