@Darkidas,
I am not a member of the Seblod development team. But I can safely say from what I know about the inner workings of Seblod that you can use any other extension's editor buttons within the WYSIWYG editor together with seblod.
Seblod doesn't change the way that data that you input with a WYSIWYG editor is saved to the Database. Only the place where it gets saved in the DB is changed by Seblod.
So yes, you should be able to use Docman's Editor button to insert links to downloadable files.
But to be 100% sure, you should ask in the Docman forum if their extension can be used together with Seblod.