Previewing PDF files in full page view

Having searched extensively for PDF related topics, questions and solutions I have been unable to find information for my small dilemma.

I have a 4k monitor so a full page preview is clearly viewable and eliminates the need to scroll within a page but I cannot find how to set the viewer pane in Directory Opus to show a full page preview by default.

I can click the icon to force a full page view but it defaults back to full width view for every new file selection. This is somewhat inefficient.

Acrobat is set to open in full page view by default.
The "ActiveX...(catch all)" plugin is ticked and is version

Is it possible to force the viewer pane to show a PDF preview in whole page view?

How PDFs are handled in the viewer pane is entirely dependent on the PDF viewer you have installed.

Opus does not include a PDF viewer of its own, it merely uses whichever PDF viewer you have installed on your system (via a plugin which acts as an intermediary and has no effect on how anything is displayed).

How the installed PDF viewer behaves and displays PDF files is entirely up to it.

You should see the same in Opus, File Explorer, Outlook and other software that can host preview handlers.

If you aren't satisfied with the PDF viewer you have installed, there are several alternatives, but it may also be worth looking at the viewer's configuration in case it allows you to change things.

Thank You Leo. I will investigate further.

How PDFs are handled in the viewer pane is entirely dependent on the PDF viewer you have installed.

I would add that Windows 7 (and presumably other releases) has not one but two ways of associating programs with files of a specific type (PDF in this case). The more familiar Default Program setting determines which program is invoked when you left-click on a PDF file from your lister (e.g., Directory Opus). However this setting does not control which program Windows (and therefore Directory Opus) uses to preview files of this type. That setting is configured via Windows' Default Preview Handler.

Default Preview Handler in turn is controlled by a Registry setting. In my case I wished to change my Default Preview Handler from Adobe Acrobat to SumatraPDF. I was able to reinstall SumatraPDF to make this happen (see Register Sumatra PDF as default Preview handler. · Issue #457 · sumatrapdfreader/sumatrapdf · GitHub).

You can configure the ActiveX viewer plugin in Opus to change that detail. (Only affects Opus, not other tools that can host preview handlers.)