Permission Denied When trying to get a file stream using _wopen() in a Metro Style App (Windows Store App)

Question

I have this issue when I trying to do something like this.

fd = _wopen(“C:\\Users\\Admin\\Documents\\paper.pdf”, O_BINARY | O_RDONLY, 0);

I also tried the download folder, but it was all the same.

Shouldn’t I allowed to access the Document folder?