Plutext

We have a requirement to attach a xlsx file to docx document or attaching a xlsx file while creating docx document. Does free docx4j community edition support this feature.
As of now we are exploring feature set of docx4j community edition

You can certainly write code to do this using docx4j, however there are no high level convenience methods to assist you.

In contrast, Plutext's Enterprise product contains an OLE Helper component to assist you with embedding objects.

If you want to write the code from scratch, you should create a sample docx in Word and examine it carefully. You can use the code generation tools to generate code from your sample docx, which will get you part of the way there. That said, it would certainly be a lot easier to try the Enterprise product.