The easiest way to create PDF-Files proabably is using a word processor and then using a tool to create the acrobat reader files - most of these programs create virtual printers for this purpose.
But there's one not so technical issue about all this. When you're talking about newsletter, I gather you mean using email to distribute it. In my experience, most users don't want mails with attachments to view in external viewers but rather a) open a link to a webpage or b) read directly in the mail client. This may be totally different for your subscribers and in the end PDF would be okay but don't dismiss this thought entirely.
So what I'm actually trying to say is that you should at least provide an immediate alternative to attaching PDF's as means of being user friendly.
Also while Ragtime or any other combinations like mentioned above are good ways for desktop publishing, have you thought about the technical means behind providing the newsletter itself? This is often the point where it becomes complicated (to inexperienced editors
). Here you'll have to decide which way to go - either you use a web-based software which often requires webspace with some kind of scripting language (Perl, PHP, ASP) or you use some desktop software which essentially works as a temporary mail server on your PC.
A lot of technical introduction may be requireable but the most professional way to combine content for a newsletter from different sources may be some kind of groupware tool or maybe even a content management system in order to publish these things on the web with only a few more clicks. In the end this might prove to be way too complicated and intense for your purposes but as you asked, an important part of creating a successful newsletter is gathering contents from different persons.
