C1PdfDocumentSource provides UseSystemRendering property that allows you to select the engine for rendering PDF files. By default, the value of UseSystemRendering property is set to true, indicating the use of system API for rendering PDF files. This increases the fidelity of the rendered PDF but does not support text selection and search.

However, you can use the basic text selection and search functionality by setting the value of UseSystemRendering property to false, which indicates the use of built-in PDF renderer.