There are many other companies that offer similar document conversion services to Docupub.com, some of which may be less expensive or offer additional features. Some examples include:

Adobe Acrobat DC
SmallPDF
Nitro PDF
Foxit PhantomPDF
PDFelement
It is always a good idea to research and compare different options before making a decision, as prices and features can vary greatly among companies. Some of the above mentioned companies may offer free version with limited functionality and paid version with more features.