Add a rectangle annotation to a PDF in Go

To add a rectangle annotation to a PDF Document page.

doc := NewPDFDoc(filename)
page := doc.GetPage(1)

// Create a rectangle
sq := SquareCreate( doc.GetSDFDoc(), NewRect(500.0, 200.0, 580.0, 300.0 ) )
sq.SetColor(NewColorPt(1.0, 0.0, 0.0), 3)
sq.SetInteriorColor(NewColorPt(0.0, 1.0, 1.0), 3)
var dash = NewVectorDouble()
dash.Add(4.0)
dash.Add(2.0)
sq.SetBorderStyle( NewBorderStyle( BorderStyleE_dashed, 6.0, 0.0, 0.0, dash ) )
dash.Clear()
sq.SetPadding( 4.0 )
sq.RefreshAppearance()
page.AnnotPushBack( sq )

Add or edit PDF annotations sample
Full code sample which shows how to add or edit PDF annotations (e.g. hyperlink, intra-document link, stamp, rubber stamp, file attachment, sound, text, free-text, line, circle, square, polygon, polyline, rectangle, squiggly, caret, and ink).