PdfRenderer is licensed per-company (or individual) and can be used in company’s products without any limitations (unlimited number of developers/deployments). Trial version can be used only for evaluation/testing purposes.
Internally PdfRenderer executes poppler tools as a separate programs (with System.Diagnostics.Process); poppler is licensed under GPL and it may be used/redistributed for free. According to GPL conditions, “aggregate” (usage and distribution of GPL-program when it is executed from another non-GPL program) is allowed. Note that if you’re redistribute PdfRenderer as part of your product, you need to declare that it depends on poppler tools as separate program and include all notices required by GPL redistribution terms.