Hi together!

I´m wondering about some entries in my phex.cfg. There are some lines like:
unstreamableSuffixes_11=pdf
unstreamableSuffixes_2=zip
unstreamableSuffixes_3=rar

Could anyone tell me please what`s the meaning of this?
Is it impossible to share pdfs for example?

Thx for help!
Max

PS: I´m using I2Phex - a modified version of phex for anonymous I2P-Network (details on www.i2p.net)