MathML equation appears as halftone in PDF

Hi,

Thanks in advance. I have a wired challenge in Adobe FrameMaker. I have created a small equation using MathML editor, and when I generate the PDF, the equations appears as half-tone image in the PDF, ie., I can't do any search in the PDF. I want the MathML equations in PDF to be searchable.

Here is the document I am referring with a small equation mathml_halftone.pdf - Google Drive

Are there any way, can I fix this issue?