PDF/A-1 is available with levels a and b. As of PDF/A-2, level u is also available. Level b is the lowest, but already guarantees the clear visual reproducibility of the PDF. This level is usually sufficient. Often, no higher level can be achieved with the existing sources. Level u additionally requires that all characters in the file also have their internal Unicode name. Note: if you need Unicode, you can do this with level b as well. He just has to use a Unicode font there. Level a is the complete standard. Here, requirements for automatic searchability are added. Objects: like headlines, images, indexes must be marked as such. This is the first step towards PDF/UA.