PDF Tools is an easy-to-use app to split, merge, compress, lock, unlock and rotate multiple PDF files in batch mode. Features include:

Compress PDF - compress images in PDF document to reduce file size.
Invert PDF - turn PDF document to "dark mode".
Split PDF - remove unwanted PDF pages and save the rest pages.
Merge PDF - merge unlimited PDF files to one single PDF file.
Lock PDF - protect PDF with passwords and all kinds of restrictions.
Unlock PDF - remove PDF passwords and all kinds of restrictions.
Rotate PDF - rotate PDF pages by 90, 180 or 270 degrees.