[upofadown]

That's why I archive my document scans as one bit per pixel PNGs. It ends up being 20KB-50KB per page at 150 PPI. I figure that there will always be a way to get the pixels out of a PNG. PDF is a more complex and dynamic standard.

[bonoboTP]

That's true, but PNGs can't have a text layer for searchability.

[zo1]

I'm pretty sure text files can reside in the same folder as PNG files.

[bonoboTP]

Yes, but not all documents are trivial to convert to a text file because the layout can be quite complex. A PDF file can have little bits of text floating anywhere and when you search inside the file, you can see it highlighted at its actual position.

[zo1]

I've had to work with PDF files before, and they're absolutely horrible. Precisely because of what you state: "little bits of text floating anywhere". Or something like disjoint, not-grouped, lines for table drawing, instead of a generic table with formatting, width/height, etc.

Though, I generally agree with you, PDF/A is quite a good way of storing documents for long-term. But, that doesn't mean that PNG files along with text files, even with x:y coordinates next to the pieces of text, aren't a feasible alternative.

[pwg]

Consider archiving them as djvu (http://djvu.sourceforge.net/). One bit per pixel djvu files at 150PPI will likely become 2-5KB pages instead.

Djvu also supports a text layer just like PDF.

Note that 150PPI is barely better than FAX, so your documents will likely look 'faxed' if you ever have to output hardcopies for some reason.

[upofadown]

Djvu is patented. As a result it is very possible that is will never achieve enough critical mass to be suitable for long term archiving.

[Spooky23]

People who worry about these things professionally generally would veer towards TIFF if PDF was insufficient. PDF/A does stuff like embed fonts and avoid proprietary compression & encryption, to avoid likely long term failure scenarios.

In the US, permanently retained documents like court records are kept in PDF. It will be around.

[upofadown]

TIFF. Often expanded as "Thousands of Incompatible File Formats".

[jahewson]

PDF is certainly more complex but its an ISO standard and even has an archival version: PDF/A.

[dalke]

FWIW, PNG is ISO/IEC 15948.