Here, Office Tab supports similar processing, which allow you to browse multiple Word documents in one Word window, and easily switch between them by clicking their tabs.
I used the code from the "Split Word Document By Page With VBA" section.
which works perfectly when I run the form directly -- correct font size, multiple lines, word wrap, etc. On runtime I turned Visibility of that textbox to False.
However, when I run the form from another userform, the text box text suddenly displays the text in a tiny unreadable font. It may take some trial and error, because the position of the Textboxes on the userform seems to matter.
I will go into the details of my approach in a follow-up post. Although it requires extensive use of VBA and may result in some performance issues, it definitely seemed to be the most flexible approach.