PDF files can be subject to various methods to protect their content. One example is adding an expiration date. For the daily processes of an organization this might be useful to avoid that people are referring to outdated content. But if you want to preserve such a file for long term accessing, this will cause problems.
This example shows a document that expired. [the text was blurred manually to protect the content, so this has nothing to do with the expiration date]. The effect is that the document can not be read anymore.
Can we prevent this?
It is important to know whether the files contain these features, before they are archived in the long term repository. This could be done either during the negotiations between the long term archive and the owner of the files. Or it could be a check that is done on the digital files while processing them for long term storage (the Ingest phase, as it is called in the OIAS model).
This picture was published on Flickr by Mark Fresco of Inforesight, who supplied me with additional information