Rangabhasyam,
We do not provide intrinsic support for third party plugins, but we will try to assist you in this case.
If you can find an archived update site of the PMD plugin which works in Eclipse Indigo, download it. Once the plugin is downloaded as zip file, Go to MyEclipse Configuration Center > Software > Add Site > Add from Archive, select the zip file and follow the wizard. You can also use the “Dropins” method to install a plugin to MyEclipse.
Here is a detailed tutorial on how to add the plugins to MyEclipse :
http://www.genuitec.com/blog/?p=1628#add-site
Let us know if you see any issues.