Provide "trim margin" feature for removing margin white space
Okular, like many other viewers, has a feature called "trim margin" which removes margin white space when viewing a document without actually editing the document. This is very useful for a number of reasons, e.g. for allowing a narrower window without accidental horizontal scrolls, which aids in placing many windows/documents side-by-side.
This is related to #439 but I thought I would add a new wish since there are a number of separate wishes in that report.