Inserting the filename is really handy in Indesign documents. It means if you are viewing the .pdf or a printed version and you need to look for it then you can see what to search for because the name of the document has been stamped into the indesign file. Even better, Indesign will do it dynamically, so that after you have inserted the filename into your indesign document if you later decide to change the filename, when you open the document up again in Indesign, the filename will update automatically (just be careful you only change the filename before it’s printed or sent out, otherwise you might defeat the purpose if inserting there filename in the In Design document in the first place!).
I can show you how with a single screenshot.
Here's how to insert a filename stamp into an Indesign document: