In future anyone that's trying to convert images to pdf's, at work we use the freeware version of cute pdf. It installs as a printer. You open the file in whatever you use to view it, and tell it to print but select cute pdf as a printer. It will then ask where you want to save the file.
Cute pdf isn't the only one out there, but it's one we use. I've also used a program called pdf fill, and the free version offers tools that allow you to merge files into on multipage pdf, and also to rearrange pages, and rotate individual pages.
John