Microsoft Word

Use cross-ref

Use a cross ref to number and link your figures, tables, and equations.

To create one: References => Insert Caption => Choose the type (figures, tables, equations, or more).

To cross-reference one: References => cross-reference => Choose the target.

Press Ctrl-A (select all) and then F9 to update all fields.

Save equations as images

MS word will become sluggish when there are too many (>50) equations in the document. It might be better to replace the equations with images.

You can save the docx document as a html web page. The equations will be converted to png images. You can insert the images to your new document.