Latexmk script could not be found

I have found a solution. I downloaded the latexmk sourcefiles from this link: personal.psu.edu/jcc8//software/latexmk-jcc/latexmk-448.zip

I unzipped the file that I downloaded, and then I copied latexmk.pl and latexmk.bat to the directory of the error. In my case the error directory was scripts/latexmk/perl/latexmk.pl I had to create the latexmk/perl/ directory under C:\Program Files\MiKTeX 2.9\scripts

Then I copied the 2 files to the following directory: C:\Program Files\MiKTeX 2.9\scripts\latexmk\perl And then I ran the MikTex update (admin) tool that came with the installation of MikTeX. I rebooted my computer and then my TexStudio was able to compile the file with latexmk.

I experienced the same problem under MiKTeX 2.9. It seems that the latexmk binary was available on my system (in Program Files (x86)/MiKTeX 2.9/miktex/bin/latexmk), but the MiKTeX package manager was not listing the corresponding package as installed. I installed the package through the package manager, and the problem was solved.