Is it possible to use ProGuard for only obfuscation. I don't want ProGuard to remove any classes from my projects. My intention to use ProGuard is only for obfuscation so as to prevent reverse engineering.
Yes, by specifying
-dontshrink
-dontoptimize
You can find details on all configuration options in the ProGuard manual.
Note that shrinking and optimization may help preventing reverse engineering a bit.