All of a sudden I can't open pdf files in memories. Why?
When you say that you cannot open them, do you mean that you cannot open them at all?
On my Mac, PDF's are working just like they always have when I was checking on them and answering a post elsewhere which you can review here: https://community.familysearch.org/en/discussion/comment/508677 (The post covers a couple of topics).
Could you explain further the trouble you are having?
I can see the pdf image but when I click on the actual document to make it bigger, it says there is an error. I have figured out if I go to "action" and download the image and then open the downloaded doc, it will open up. But I doubt most people will know how to do that. I have never had to do that before until now.