How to Permanently Rotate a PDF file

Have a look at the http://www.pdfclown.org[^] library (licensed under LGPL and can be interfaced from C#). It has support for rotating PDFs and seems very simple to handle. I was able to construct the following example quite easily without knowing the library:

public bool Rotate()
{
    File file = new File(@"D:\sample.pdf");

    foreach (var page in file.Document.Pages)
    {
        page.Rotation = RotationEnum.Rightward;
    }

    file.Save();
    file.Dispose();
    return true;
}

In detail, this is about setting the "Rotate" key in each "Page" dictionary in the document which is a minimalistic change to the document. Saving the file however might do other changes (such as choosing other compression algorithms, removing unneeded objects from the PDF document, ...).

The most dominant problem I can see is that such libraries always lag behind the PDF standard and therefore will not work with all PDF documents. But it might work with documents from a specific source.

Another alternative might be the http://www.quickpdflibrary.com/[^] which is available in a free-to-use lite version.

There is also the http://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/[^] which comes with a ready to use tool for PDF rotation.