That would be the most important question- security. Is this something you want to lock that no one can edit, copy, or steal? If so, PDF would be the best. Of course you would need to buy expensive software to do so, and learn how to use it. Also, those who want to view it may need PDF Viewer (free software, but something someone would need to install on their computer before being able to view it I believe).
If security is not an issue, the simplest way is to scan, or if you are pretty good with a camera take pictures of the pages, then use any photo software to convert them into JPEGS and load them into a PowerPoint. Of course they would need to load PowerPoint Viewer on their computers as well, and you would need a copy of PowerPoint from Microsoft Office.
I love using MGI PhotoSuite to prosses all of my pictures. It's easy to use, and can crop, edit, touch up, do artsy things to them, resize them, convert them into JPEGS or other formats, add text, and make collages. All for about $30 (last time I bought it).
Click Here for a review
I use the Platnum version
Here's one on eBay