1. Install Libreoffice
    URL : https://www.libreoffice.org/download/download-libreoffice/
    Version : 25.8.3

2. Add in system variable path : C:\Program Files\LibreOffice\program\soffice.exe (might change according to your PC configuration)

3. Add the path in doc2pdf file

4. If you see a popup waiting for printer, Go setting > Printer & scanners and set a printer as default or Microsoft Print to PDF