Problem Protect PDF after split page by page

After I had used feature "Split page by page" (PDF24 launcher --> File Tools --> Split page by page), and then I was used "Lock PDF" (PDF24 launcher --> File Tools --> Lock PDF), there was not found any files in save as folder.

Lock PDF without using Split page by page before, not make this kind of problem.

Hopefully PDF24 team can fix this problem soon. Thanks.

Regards,

eddy