One easy way to convert an image into a PDF file is to use a virtual PDF printer or file conversion software such as Omniformat. But what if you have a collection of images that you want to consolidate into a single PDF file. This is where a general file conversion utility fails.
i2pdf is a free and portable software that was created specially for this purpose. Simply drag the images into the program window and click on the Build PDF button.
There are options that allow the user to tweak the output - control image quality and size, create thumbnails and adjust page layout. The supported image formats are: jpg, png, bmp, tiff and gif.
Related: Extract images from PDFs