I am working on an online portal, where researchers can upload their research papers. One requirement is, that all PDFs are stored in PDF/A-format. As I can't rely on the users to generate PDF/A conforming documents, I need a tool to check and convert standard PDFs into PDF/A format.
What is the best tool you know of?
Price
Quality
Speed
Available APIs
Open-source tools would be prefered, but a search revealed none. iText can create PDF/a, but converting isn't easy to do, as you have to read every page and copy it to a new document, losing all bookmarks and annotations in this process. (At least as far as I know, if you know of an easy solution, let me know).
APIs should be available for either PHP, Java or a command-line-tool should be provided. Please do not list either GUI-only or Online-only solutions.