Convert whole pdf to single png

I want to convert my whole pdf to a single png, but the examples I found can only convert a selected page of pdf. Can you give me a example how to do so.

@guguzzz

Can you please share your sample PDF for our reference? Also, please share if you have Aspose.Total license? We will further proceed to assist you accordingly.

Any pdf more than 2 pages can be the sample, I just want to montage the pages and get a long png. Part of my license as below,
image.png (58.8 KB)

@guguzzz

We have opened the following new ticket(s) in our internal issue tracking system and will deliver their fixes according to the terms mentioned in Free Support Policies.

Issue ID(s): PDFNET-54975

You can obtain Paid Support Services if you need support on a priority basis, along with the direct access to our Paid Support management team.