To create a graphic watermark or identity plate for this purpose with a hand written chalk look you would need Photoshop or Elements to create a transparent PNG file so you might as well do the whole thing in one of those programs to start with. You can't do this in the develop stage anyway like you requested.
...so, Apple Pages is better for making poster or post cards than the highly overated PHOTOSHOP CRAP by the famous God-like ADOBE?? REALLY?
and to think it used to come embedded on all Macs! Seriously, what about wrap around fonts? Not on Lightroom 2 or Elements 10?
I am with you, I am wanting to create posters, cards and flyers with custom texts. I can't stand all those pre made "templates" What about creativity? Surely I am missing something?