Please take a look at the Rotate90Degrees example.
In this example, we create a
PdfDocument to get an instance of the document, and just change the
/Rotate value in every page dictionary (if there is no such entry, we add one with value 90):
PdfDocument pdfDoc = new PdfDocument(new PdfReader(src), new PdfWriter(dest)); int n = pdfDoc.getNumberOfPages(); PdfPage page; PdfNumber rotate; for (int p = 1; p
Once this is done, we use
pdfDoc.close() to persist the change.
If you want an iText for C# example, you'll discover that it is very easy to port the Java to C# as the terminology is identical.
Click this link if you want to see how to answer this question in iText 5.