There is a newer SDK available for cloning at:
https://github.com/pocketbook/SDK_6.3.0.git
It is different from the older SDKs, so more stuff to learn. I guess step 1 is figuring out which of the three architectures available matches your ereader. I don't remember the details, but I probably looked at /proc/cpuinfo on the ereader, and then googled the Hardware: field to see which SoC it used. For example, my PB Color says "Hardware : sun8iw10", and googling "sun8iw10" shows that the SoC is "B288", so I used the SDK-B288 tree for that.