Once you have the paper, it will appear blank in your inventory until you expose it to .
The secret text will reveal the storage password: 1371 .
Inside the office/storage room, there is a switch on the wall that turns on a purple UV light.
You must reach the office area by using a bolt cutter to release a minecart that breaks through a wall.
Detailed walkthroughs for these sections are available on GameFAQs and the Penumbra Wiki .