The PDF engine used in Google Chrome, called PDFium, is open source under the "BSD 3-clause" license. I believe this allows redistribution when used in a commercial product.
There is a .NET wrapper for it called PdfiumViewer (NuGet) which works well to the extent I have tried it. It is under the Apache license which also allows redistribution.
(Note that this is NOT the same 'wrapper' as https://pdfium.patagames.com/ which requires a commercial license*)
(There is one other PDFium .NET wrapper, PDFiumSharp, but I have not evaluated it.)
In my opinion, so far, this may be the best choice of open-source (free as in beer) PDF libraries to do the job which do not put restrictions on the closed-source / commercial nature of the software utilizing them. I don't think anything else in the answers here satisfy that criteria, to the best of my knowledge.