Yes, XML is one of the formats Excel generates so when you pass a file with .xml extension, it thinks it's an Excel generated file and tries to load it as that.

 

For regular XML files, you can specify the format explicitly as DocumentFormat.Txt and this way DocumentUltimate can interpret it as a text file. However as of current version you can only specify format when you use DocumentViewer.DocumentSource or DocumentViewer.DocumentHandlerType properties. Maybe we should add a new property DocumentViewer.DocumentFormat so that it can be used along with DocumentViewer.Document.

 

By the way, why do you need to use DocumentViewer for viewing XML files? As far as I know browsers can already display XML files with syntax highlighting which seems a better fit.

FYI, we have released 3.15.5:

So now you will have the ability to override the document format like this:

 

documentViewer.Document = @"c:\SomeFolder\Document.xml";
//Force "Document.xml" to be treated as DocumentFormat.Txt
documentViewer.DocumentFormat = DocumentFormat.Txt;

 

However, there still seems to be a problem specific to converting XML files (it's a text file but the tags in it currently confuse the converter so the generated PDF has no pages). I just wanted to let you know about the new property (at least you can use it for other formats that you want to treat specially) and we will fix the XML specific issue in the next version.