The point of the Resources folder is to tell Unity that everything in it must be packed in the final .unity3d, whereas the other assets are packed only if a GameObject is using them explicitely. Conclusion, there is no Resources folder once the game is built.
build
After that the .pdf file should be locate in the resources folder (project_folder/build/project_name/resources), because the file don’t will be there, you can’t open it.
I don’t now how can attach this file to a scipt. Asset bundles how works?