using (var doc = PdfDocument.Load(@"e:\49\SampleFile.pdf"))
{
    foreach(var page in doc.Pages)
    { 
        foreach(var pageObject in page.PageObjects)
        {
            var textObject = pageObject as PdfTextObject;
            if (textObject == null)
                continue;

            check the textObject.Matrix here
        }
    }
}