Unlock pdf file?
 

I download a pdf file but it's locked... do you know how to open it?

pdf's can be tricky. If it's been encoded as closed then there's little you can do except edit it with a program like illustrator or freehand. If it's simply a case of locked file, then depend upon your os. On mac it's easy to unlock a file, on windows i'm not sure, same with linux.