Which converter should I choose (BMP->PNG, TIFF->PDF) to watch directories?

Question

Data conversion

There are different programs for monitoring the directory and if a file appears in it, then convert it to the specified format.
There is ABBYY FineReader 11 Corporate Edition with the Hot Folder function, but it has a limit of 5000 pages and it only converts to PDF, but you also need graphics.
I can write a program that will monitor the directory and run external utilities to convert the files that appear, but I don’t want to reinvent the wheel.
Perhaps there are already successful implementations?
You need to:
1. Keep track of two directories.
2. Content if it appears convert BMP->PNG, TIFF(multi-page) -> PDF

Answer 1

Do they support command line work?