How to generate the PDF in CQ5.6.1. I have a page with from with some fields and need to generate the PDF whic contains all the form field and its values.

Using AEM to generate PDFs - you have two choices for this type of workflow:

1- If your enterprise requires true PDF integration, it may be worth looking at the possibility of integrating AEM with LiveCycle:
http://helpx.adobe.com/livecycle/help/aem/aem-livecycle-connector.html

http://scottsdigitalcommunity.blogspot.ca/2012/07/integrating-livecycle-into-adobe-cq.html (this shows integrating AEM and LC and creating a PDF/A document for long term storage.)

This is an enterprise scale solution and you will be able to perform all sorts of PDF/AEM solutions to address many enterprise use cases.  

2- You can also use a PDF Java lib like PDFBOX to create a custom OSGi service that generates PDF documents. See this community article: 
http://helpx.adobe.com/experience-manager/using/creating-custom-experience-manager-pdf.html (PDFBOX API is not a substitute to LC server - but it will generate PDFs). 

But there is no documentation that discusses how to configure AEM to generate a PDF with both forms and form data. This is not an out of the box feature.