Your problem is that you are trying to use wkhtmltoimage.exe to create a PDF file. Use wkhtmltopdf.exe and everything will be fine.
C:\Program Files\wkhtmltopdf>wkhtmltopdf.exe www.google.com go.pdf
As for your question, I really do not believe that there is an ideal tool. However, I was very pleased with wkhtmltopdf.
source share