I found a solution. In the Mint System settings--Font Settings, I switched to 1.3 text scaling factor. This blew up the size of everything in Vivaldi, including the drop down lists. Then I had to go to the controls within Vivaldi and reduce the User Interface Zoom down to 130%. This makes the controls an acceptable size and retains the larger fonts in the drop down lists.
Text size in messages is fairly large now, and I may play with the UI Zoom a little, but this combination seems to be working ok.
Thanks for pointing me towards the system controls and I appreciate all the replies, trying to help me through the problem.
(Notice one fine point here..: WHY do I want to print to PDF in the first place? a) I need to highlight text in longer pages/documents which I would like to return to later and only read what is highlighted - to save time, AND also, b) I want the possibility to share the highlighted text with others, either privately or in public. That extra step via PDF would be unnecessary if the browser could provide highlights etc. (such as what Diigo.com does, for example), but with LOCAL STORAGE and NO data transferred to or stored outside of the computer. Then we could integrate a send-via-email feature to share with others, and even one that could let us save/share a page in the cloud or the like, but the default must be that we work securely locally by default.)
I have 56 bookmarks in my Opera Bookmarkpanel on the right side (14" FHD).
In 6 years i didnt click once on a wrong bookmark.
Total waste of time such big spaces and fontsize.
Mod Edit: Disrespectful comments removed.