Removing last page from document results in error

I'm generating pdf files based on database info. I'm not clear why, but currently it appends a single blank page to the end of the completed document. I was hoping to just delete that final blank page, but when I try I get a "stream is not writeable" error.

Here's how it's coded right now:

var pdf = new Pdf();
var section = pdf.Sections.Add();
var marginInfo = new Aspose.Pdf.Generator.MarginInfo();
marginInfo.Top = topMargin;
marginInfo.Bottom =  marginInfo.Left = marginInfo.Right = MarginOneInch;
section.PageInfo.Margin = marginInfo;           
section.TextInfo.FontSize = 12;
section.TextInfo.LineSpacing = 1.5F;           
Aspose.Pdf.Generator.Text t = new Text(stringBuilderContainingInfo.ToString());          
t.IsHtmlTagSupported = true;           
section.Paragraphs.Add(t);
pdf.Save("c:\someFileName.pdf");
Document d = new Document("c:\someFileName.pdf");
d.Pages.Delete(d.Pages.Count);
d.Save();

Why does this not work?