Thank you so much for responding.
Based on your advice, I redirected the path of the Build Files to the build.xml file in the dita-ot folder. (Image is attached for your kind reference)
I made sure that all the instructions mentioned in your book are followed. But still, the PDF file is not generated in the output folder, but the build is successful.
I have attached the following:
You had advised to upgrade to v2.5.4. (But the full install version is not available for this version.I guess only the minimal version is available to install and that does not have the build file. It just has some folders. In that case,do i need to copy the build.xml files from a fully installed version and paste it to this version.)