I took al fast look to Help:Djvu pages (with different names into different projects) in Commons:, en.source, fr.source; I found interesting suggestions about djvu files but I didn't find a detailed help about djvu text layer, nor about its manipulation. So, I imagine that such a page could be really written by scratch to share needed details. Where? What are your suggestions for its name? I found that wikisource.org has a poor setting of help pages; I presume that not so many users browse it; is perhaps Commons the best project to collect scripts, tricks, ideas?