Converting only 2 pages is taking more time using headless mode

I have a docx file which contains approximately 7500 pages, converting this document to pdf is taking around 26 mins in headless command line mode.
I wanted to do it in chunks to get the better performance for the user i.e., atleast convert the few pages first and then remaining pages later.
So, I tried to convert the first 2 pages using --convert-to pdf:writer_pdf_Export:{“PageRange”:{“type”:“string”,“value”:“1-2”}}
but the problem is converting the first 2 pages also taking around 15 mins. so it looks like it need to process/load the entire document for converting the few pages .

Is there a way to make this faster atleast for few pages ?

Regards,
Satya