Regardless of the size of the XML, the application will always use about the same amount of memory to view the file.
The document has about 2.5 GB and more than 39 million lines of XML data.
Also, a commenter below points to this more complete wrapper utility.
You could also use xmllint, which is part of libxml. Example usage: One problem is that libxml doesn't implement all of the specification, so you may run into issues :( Alternatively, if you are on Windows, you can use msxml, but you will need some sort of wrapper to call it, such as the GUI one described in this DDJ article.
Note that any text editor can edit XML, so this page only lists software programs that specialize in this task.
It doesn't include text editors that merely do simple syntax coloring or expanding and collapsing of nodes.