PDF/A - ISO Standard for Long-Term Archiving

A key element to this reproducibility is the requirement for PDF/A documents to be 100 % self-contained. All of the information necessary for displaying the document in the same manner every time is embedded in the file. This includes all visible content like text, raster images, vector graphics, fonts, color information and much more. A PDF/A document however is not permitted to be reliant on any information from direct or indirect external sources, for example links to external image files or font that are not embedded.

Why do you need PDF/A? 

The PDF/A standard for long-term archiving was adopted by ISO (International Standards Organization) in autumn 2005. The PDF/A standard aims to enable the creation of PDF documents, the visual appearance of which will remain the same over centuries. It is conceived for users who want to be sure that their documents contracts, invoices or technical documentation are legible and useable even after 10, 50 or 100 years.

That the inventor of the PDF format, Adobe Systems, has revealed its format implies for users and developers, an assurance that programs will be available for generation and display of PDFs even after decades. However, only the PDF/A standard can guarantee that users will be able to view exactly the same content as when their documents were created.