We have been using this product for a year. Generally good. However, had a problem and I had to get componentsource.com involved for them to sort it out. Also, this product do NOT support all PDF files which is not displayed on either this or their website. I emailed them a PDF file and got the following response:
The file you sent uses a PDF shading (gradient) for the background and PDFView4NET does not support this feature, this is why the page appears blank.
We plan to support PDF gradients in future versions of PDFview4NET.