What are some free tools that will allow someone to split PDF files using the software's API in .NET? (not by using the software over a command line interface). Not looking for shareware which may have watermarks etc.
Essential PDF can be used to split PDFs : C# sample. The sample linked to here is ASP.NET based, but the library can be used from Windows Forms, WPF, ASP.NET Webforms, ASP.NET MVC, Silverlight, WinRT, Windows Phone, Windows store Universal and Xamarin applications
The whole suite of controls is available for free (commercial applications also) through the community license program if you qualify. The community license is the full product with no limitations or watermarks.
Note: I work for Syncfusion.