There are items/options that can be used within a given PDF that will drastically affect how likely it is that the PDF will still be readable. * Inclusion of 3D applets or any Adobe Acrobat specific features I have seen PDFs with 3D chemical applets embedded somehow into the PDF using a plugin. The longevity of this addon depends entirely on how long the company/team that made the plugin, wants to support it. * DRM of any kind - password-protected, print-disabled, etc These features make it hard, verging on the legally impossible to migrate the PDF to a newer format or read it on newer versions of Acrobat or other PDF viewers. (Legally impossible, as circumventing this would incur the wrath of the DMCA) * Any other odd features. There is a profile, which doesn't allow you to add any of the above, and it is often referred to as PDF/A (A for Archival format) The easiest way to create these at the moment, is to use OpenOffice 3 and choose the "Save As PDF" and tick the PDF/A option. As for not becoming unreadable.. well, this all depends on age (and so the version) of the PDF, and your current viewing software. I have already had situations where older PDFs cannot be viewed correctly in newer readers (majority of these were due to older 'print-ready' pdfs with colour-information held within) And this doesn't include the various issues that can arise from fonts not being included or present on the client's system, 'print' fonts that compress letters in interesting ways ("fi" -> single character, but a non-unicode one), images that do not display, incomplete PDFs due to bad exports that silently fail, etc. My advice is to keep the source files alongside, especially if they are in (la)tex or HTML. Text is always parsable. Ben On Mon, 2009-06-15 at 11:37 +0100, Mike Taylor wrote: > Dear CODE4LIB colleagues, > > In one of my alternative incarnations, I am a zoological taxonomist. > One of the big issues for taxonomy right now is whether to accept as > nomenclaturally valid papers that are published only in electronic > form, i.e. not printed on paper by a publisher. > > In a discussion of this matter, a colleague has claimed: > > > [PDF files will not become unreadable] in the next 30-40 years. > > Possibly not in the 20 years that will follow. After that, when only > > 30-year and older documents are in the PDF format, the danger will > > increase that this information will not be readable any more. It is > > generally considered as quite unlikely that PDF will be readable in > > 100 years. > > I would appreciate any comments that anyone on this list has on the > likelihood that PDF will be unreadable in 100 years. > > Many thanks, > > _/|_ ___________________________________________________________________ > /o ) \/ Mike Taylor <[log in to unmask]> http://www.miketaylor.org.uk > )_v__/\ "Can't someone act COMPLETELY OUT OF CHARACTER without arousing > suspicion?" -- Bob the Angry Flower, www.angryflower.com