There have been tons of answers posted in other threads on the topic so you may want to browse and search a bit more, but what worked for me was a letter from my Chief Pilot confirming my flight time with the company (only had a letter from my last job) and then copies of my last sim check. Did not have the originals like they asked for. That seemed to suffice...
They specifically said that notarization would not meet their needs if anyone is thinking about going down that road...