FT Signature plugin - signature on selected posts only

I want to be able to place a signature on selected posts and pages only, which is exactly what this plugin is supposed to do, as discussed on this closed thread.

At first glance it seemed to perform exactly as advertised; however on closer inspection it only seems to work for posts on the first page of the loop and I don't know why that is.

Secondly, I'm not sure how to get it to work on pages. I presume it's something to do with the Custom Fields section, as I can see an 'ft_signature_manager' option. But what value do I enter to get it to show? I've tried what I think is the signature file, which is ft_signature_01, but nothing is showing.

Sorry if I'm being dense about this; I've read through the Custom Fields bit in the WP codex but it's not proving very helpful in this case. I'd really appreciate some help to get this working. Note that I'm not brilliant at coding so please be gentle with me when explaining what I'm doing wrong! :-)

thanks, Grum

(WP3.0.1, ATA 3.5.3)