They came on the same day!!
Although CBS obstructed the investigation in every way, it was commendable that they published the PDF documents on their website.If CBS had followed the normal practice of the major news media, the reporter would just waved some papers in front of the camera, or flashed a illegible picture of the memo on the screen during their report. In the vast majority of cases, the networks do not provide a full scale electronic copy of their evidence on their websites.
If CBS had not taken the unusual step of web publishing the (phony) memos, their authenticity might not have been questioned.
Here is the big question - How many more forgeries would be uncovered if the news media followed a policy of web publishing the memos they cite in their reports?
If CBS News sincerely wants to restore their credibility, they should publish every document they rely on in their reports (unless it contains sensitive national security info, of course).