We have some legacy HTML content which we must render in compatibility mode. The requirement comes from our customers who want their HTML-based reports (some of which were c
This is a pseudo-answer to your slightly non-specific question;
In regards to your apprehension to rely on this IE feature for "back-compatibility", I feel the same way. Microsoft has provided this option because there are lots of companies out there who take a long time to update their web content. This option is meant to allow them to have a quick and dirty stop-gap, not a permanent solution.
So, what's the permanent solution? If that is your question, then IMO this is the answer; don't rely on the stop-gap and develop the correct output for the reports.
Without knowing what those reports are it is impossible to properly advise you on that part, but here's a stab in the dark:
There are lots of options to convert "HTML" to PDF. (I put HTML in quotations because each rendering engine is bound to require different versions/standards of HTML and you'll need to know those assumptions before you pick one.) If you want output that will format 100% the same on any browser, then you want a format that is meant to be static and not change; like PDF. Plus, then you also have the printing options taken care of as well.