How can i upload an attachment its extention is word Or PDF and how can i save it on my iphone to upload it anytimew

How can i upload an attachment on safari and its extention is word Or PDF and how can i save it on my iphone to upload it any time , is there any app helps ???!

when i am on safari and i click the upload button it always takes me to my photo library so i tried to screen shot my attachment but the web site shows me an extension error and i cannot change the screen shot extension, it must be a solution exist??!