Resolved Preview unexpectedly opens pdf file, which subsequently can’t be closed.

Suddenly Preview is giving me grief.

When I open a pdf file, Preview opens another (unwanted) pdf file first before displaying the requested pdf.
So when I open one pdf, Preview displays 2 files: the unwanted pdf first, and the requested pdf second.
It’s always the same unwanted pdf that’s opened.

Then, to add insult to injury, I cannot close the unwanted pdf !
When I press the red close button to close the unwanted pdf, it does not close.
The requested pdf does close normally by pressing the red button.
The only way to close the unwanted pdf is by quitting the Preview application.

I've been trawling the internet for hours for an answer but can't find one on this one !
Thanks,
Art

Solution found by deleting .qxd file linked to .pdf