free alternative to iTextSharp
The AGPL basically states that you can use iTextSharp if any user of your application can have access to the source code of both iTextSharp (along with the possible modifications you did on it) AND your application under the AGPL terms. If you want to be released from these requirements, you have to pruchase a license from iText.
You'll find more information here.
If any doubt, don't hesitate to contact the sales department of iText.
So, in short Version 2 you can use without payment (standard library open source license). For version 5 you need to pay iText.
There are multiple options.
PDFSharp
You could try PDFsharp it has an MIT license which means according to what it says here you should be able to use in a commercial product.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
FreeSpire.Doc
There's also FreeSpire.Doc (on NuGet), which is limited to 3 pages and 500 paragraphs. It can convert Word documents to PDFs.