For my phone iAnnotate (full version) is a paid app. Did it come pre-installed in your phone? For me the free version (iAnnotate lite) is available through Samsung Apps, with the option to upgrade to the paid version.
I am much more impressed by EZ PDF Reader than by iAnnotate. The features list for EZ PDF is huge, and it would take longer than I wish for me to list everything. Additionally, once iAnnotate was done with a file I could no longer open the file with any programs other than iAnnotate or Adobe Reader. Everything else (PDF to Go, Polaris Office, EZ PDF Reader) saw the files modified by iAnnotate as being corrupted or would open them but not show any of the annotations (Kindle Reader).
Does this differ from your experience with iAnnotate?