To rotate a page in a PDF document.

doc = PDFDoc.new(filename)

# Rotate the first page 90 degrees clockwise.
page = doc.GetPage(1)
originalRotation = page.GetRotation()
rotation = nil
if originalRotation == Page::E_0
  rotation = Page::E_90
elsif originalRotation == Page::E_90
  rotation = Page::E_180
elsif originalRotation == Page::E_180
  rotation = Page::E_270
elsif originalRotation == Page::E_270
  rotation = Page::E_0
else
  rotation = Page::E_0
end
page.SetRotation(rotation)

A page can be rotated clockwise, by 90 degrees, when displayed or printed. The Page.GetRotation() method returns the Page.Rotate enum specifying the current rotation. Similarly, Page.SetRotation() sets the current rotation.