I cant open a pdf file in my adobe acrobat reader

I do a lot of Photoshop and some times I need to use a photoshop pack. Some of then are pdf files and whaen I wanna open it, its says :

adobe acrobat reader could not open your file because the file type is not supported or the file is corrupt (it was sent as an attachment and was not decoded correctly, for example).

And the other Photoshop packs that are a pdf file do not work.

Please help me 

I speak French so if there a person how speak French, please help me!!