@snehalghute You are right, there is no public API to get footnote id, because it is not stored in the Aspose.Words Document Object Model. The
id attribute is used upon reading to associate the
footnoteReference with the appropriate
footnote from the
footnotes.xml. Upon writing the document to DOCX, the ids are generated on the fly. So if, for example, there are 3 footnotes in your document and you remove the second one in the output document you will get 1 and 2 ids of the remaining footnotes. MS Word behaves the same way. So footnote id is unique within the document, but is not guaranteed to be be the same upon the document lifecycle.
If your requirement is to identify nodes within the same document, you can consider using Node.CustomNodeId property. But you should note, the specified value is not saved to an output file and exists only during the node lifetime.