First test is to open the PDF in Adobe Acrobat Reader, and to use the text select tool. Select all the text, copy and paste it into Notepad. If that still gives you strange characters then it's clear that the problem is the PDF encoding and not Monarch's interpretation of it.
Second test is to experiment with the different PDF import options for your version of Monarch, as some known problems are fixed by these.
If you still have problems, then it sounds like PDF Creator isn't doing a very good job. Perhaps check the settings in PDF Creator for embedding font information in the PDFs it creates to see if you can change these?
If you don't have control over the PDF creation, and just need to sort the data out, I recommend www.pdftransformer.com[/url] where you can download a free trial of PDF Transformer by Abbyy, which will let you make a clean PDF that Monarch can read.
If you have Monarch v10 Pro, perhaps printing to PDF to XPS would be another option worth exploring?