Make a copy of this page by calling it "newpage.htm" or whatever you want and saving
in the info/sidepanel directory with all the other factsheet pages, but make sure you save it as .htm.
(You'll notice that this addpage.htm is in there)
Then when you want to create a new page all you have to do is create your link like this:
factsheet.php?factsheet=newpage (you don't need to add the .htm bit)
This will allow you to create any number of pages you like which will be 'pulled into the factsheet page'
So if I wanted to create a page called links.htm I'd open up this page from
the info/sidepanel directory, change the text and then save it as links.htm.
The link to it would be:
factsheet.php?factsheet=links