You should probably look at Migradoc to accomplish this. I would imagine the steps you are:
Load your PDF into a Migradoc Document object.
You can then iterate through each section within it. (I have not tried importing a prec-reated PDF file into Migradoc so not sure how this works)
Assuming you get this far you can then iterate through each Element within the section which would look something like:
Code:
List<string> allText= new List<string>();
foreach (DocumentObject element in Section.Elements)
{
if (element is MigraDoc.DocumentObjectModel.Text)
{
MigraDoc.DocumentObjectModel.Text textObj =
(MigraDoc.DocumentObjectModel.Text)element;
allText.Add(textObj.Content);
}
}