Do I need to do more prep work on this cement floor before putting in new tile?
The paper backing can be cleaned off with a solvent paint stripper and then wash the old glue off with trisodium phosphate and a scrub brush. Then wash several times with water to remove the residue of both operations. Tile thin set in most cases may not adhere to old glue, especially if you have to use unmodified thin set because you are planning on using an uncoupling membrane like DITRA.