Preview suddenly won't open .pdf files but Adobe Rdr. will
I have suddenly developed a strange problem with Preview:
Recently downloaded .pdf files (from tech manual sites; several different sites), (files that were never opened in my browser but just downloaded by clicking a download button and having the file drop into "Downloads") will NOT open with Preview (my default viewer)
When I click on them I get a message that I can't open the file because is don't have "Permission". But if I check in "get Info", I DO have permission! Unlocking the permissions and resetting them to "read & write" for me (by log-in name), "staff" and "everyone," makes NO difference. Still get "No Permission" from Preview!!
Although Adobe Rdr. is not my default reader, if I open the same .pdf file with Adobe Rdr. it opens fine! No permission problem.
In at least one case, when I try to open (w. default Preview), I get the message that I can't open the file because my Preferences are set to not open "Apps" from "unknown publishers"!! And this for a .pdf file!! If I try to open that same file with Adobe Rdr. I get a caution warning that this "App" is from an unknown publisher and am I sure I want to go ahead?? If I click continue, then .pdf then opens in Adobe Rdr. just fine!
I find this combination of behaviors bizarre and baffling! Old .pdfs that I've had in my system SEEM to open OK, though obviously I haven't tried every one!!
Anyone have any suggestions as to what's going on or how I might fix this??
iPhone 4, iOS 5.1