libharu:HPDFDoc#set_open_action
#!/usr/bin/env ruby require "hpdf" pdf = HPDFDoc.new page = pdf.add_page d = page.create_destination d.set_fit() #d.set_fit_h(0) #d.set_fit_h(100) pdf.set_open_action(d) pdf.save_to_file(File.basename($0, ".rb") + ".pdf")