I am using PDFLibNet.dll (got here: http://www.codeproject.com/KB/applications/PDFViewerControl.aspx?msg=3154388 ) am not sure whether I can use it for commercial purpose (Licence) ?
Any help is much appreciated.
You're not going to get a definitive legal statement from anyone here. But -
Unfortunately that code uses lots of extra libraries that all have separate licences. From a quick glance you've got
So you'd need to buy commercial licences for a couple of components unless you're willing to release your source. Depending on how you're using the library you may be able to remove those components instead, though.