VS 2019 Combine PDF Files in VB Net

I have created a number of pdf files that I wish to combine into one
I have the titles stored in a "sFileName() as string" array
I am looking for a routine that will read this array and add them to a new file.

I have loaded the following library, but can't seem to figure how to use it.
Imports iTextSharp.text.pdf

Thanks
Richard