Recasto allows you to quickly convert PNG, JPEG, TIFF, BMP, and many other image formats to PDF, as well as PDF to images. Just drag-and-drop images or PDF files (or even PDF pages) from Finder, a web browser, PDF editing software or Preview. After that, Recasto will come up with various set-up options to achieve the best conversion result for you. For example, images can be rotated or flipped before conversion and while converting PDF to images you can adjust the DPI level to your liking. Images can be merged into a single PDF file, or Recasto can create a separate PDF for each one.
Please note that Recasto supports locked/encrypted PDF files, but in order to process them, you will have to enter the correct password for each locked PDF file.
In general, the app is pretty simple to use and gets the job done. All buttons and UI elements have tooltips, and in case you have any questions, I'm always at your service firstname.lastname@example.org.