Thank's for your efforts, and I just wish that this was the solution. Unfortunately, it isn't because, after double-clicking on the pdf in the website, it simply "opens" in another Safari window as a black screen - the pdf is there, somewhere, but not visible (either as an icon, or as a document).
When I right-click in the black Safari window, where the file is supposed to be, the only option available to display the file is to "Open file in Internet Explorer" (which is not what I want to do). Other options include saving or printing the pdf, which I don't want until I've confirmed that it's the form that I want. The same options are offered if I right-click on the file icon in the website.
Any other suggestions, please?
does Safari - Help - Installed Plug-Ins show some pdf viewer, other than WebKit built-in PDF ?
often it's an adobe plug-in(s), but whatever it is doesn't seem to work, and needs to be removed from
/Library/Internet Plug-Ins/ or the same folder in your Home Library.
A few sites don't work well with pdf's & safari - can you see these as expected ?
If so, the other site is likely causing a problem. If not, likely a plug-in as described above.
Thank's for your persistence, it's very much appreciated. Installed Plug-ins includes a comprehensive listing for pdf (including Adobe Acrobat), as well as the WebKit Built-in PDF.
Following on from your earlier advice, should I remove these from /Library/Internet Plug-ins (and I'm assuming that they would be replaced, somehow)?
This is delving into the "deep and dark", for me, so I won't try anything until I hear from you.
quit any open browsers, then trash the file(s) with pdf in the name from .../Internet Plug-Ins/ - you'll normally be asked for an admin name/password.
Then locate the file(s) in your trash folder & drag them out to a folder of yours, or the desktop - then you can readily replace them later if necessary for some pdf's that don't display with the built-in.
You should now find that Safari - Help - Installed Plug-Ins shows only the built-in, and that pdf's at apple display norrmally in Safari