It appears that mcf to pdf conversion is typically related to export of My CEWE Photobook projects to PDF format, typically for printing purposes. You can use the mcf2pdf utility that was designed exactly for the purpose of exporting My CEWE Photobook files. You can download it from GitHub and convert mcf to pdf.
The generated PDFs are NOT, and will never be, a 100% representation of the designed photobook. Also, they do NOT include bleed margins (especially not for the cover pages) and such things, and they use the RGB color model, not the CMYK model used for professional printings.Open MCF file Open PDF file
A converter for My CEWE files