Photo Contact Sheets does one thing simply - it creates PDF contact sheets of folders containing JPG and PNG files sorted by filenames and labeled.

Simply,
1) Pick a page size, Letter or A4,
2) Choose 3, 4, 5, or 6 thumbnail columns,
3) Select the resolution of the thumbnails (huge influence on the final PDF size),
4) Select the folder containing your selected photos, and finally,
5) Tell the app where to save the PDF Photo Contact Sheet.

That's it. No other options. No preferences. Just gets the job done.