HTML5 and PDF have two different view on the concept of "document". Please note, that PDF is based on PostScript, which is a complex programmable descriptive language for printers. The web for which html5, css3 and other things bootstrap relies on are living in a totally different world.
So mapping some content and format between html and pdf is a matter of convention you have to decide, and eventually implement. The tools you have referred to or
MvcRazorToPdf[
^] are doing this in their own way. Either way, they read the html content, interprete the format and generate pdf primitives. Bootstrap is to complex, too dynamci and too new to have a ready-made mapper to use. So you either do it yourself, or accept the constraits of the existing tools.
You shoudl read these too:
http://daveaglick.com/posts/using-aspnet-mvc-and-razor-to-generate-pdf-files[
^]
Generate PDF in ASP.NET MVC Using Rotativa[
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