When I see a perfectly adequate answer destined to go unrewarded because it’s the only answer, I assume the asker has “abandoned” the question. This is unfair to the answerer, so I post this “answer” to release it for voting. I would hope others do the same.

If you have the full version of Adobe Acrobat you can add as many pages as you like, as well as controlling page size. You can use Adobe Acrobat very much the same as you might use Microsoft Power Point, except Adobe Acrobat will preserve the quality of your images, and not dumb them down to a low resolution Windows Metafile like Power Point.

You could also combine your images in Photoshop on one canvas before you save them as a PDF. And yes, Adobe Reader, does only that, it just opens PDF files, without editing capability.