Flatten

Basic Flatten

Open a filled form PDF and flatten all fields into static content.

doc, _ := gpdf.Open(filledFormPDF)

if err := doc.FlattenForms(); err != nil {
    log.Fatal(err)
}

result, _ := doc.Save()

Flatten + Watermark

Flatten form fields and add a "FINAL" watermark.

doc, _ := gpdf.Open(filledFormPDF)

// Flatten forms
doc.FlattenForms()

// Add watermark
doc.EachPage(func(_ int, p *template.PageBuilder) {
    p.Absolute(document.Mm(50), document.Mm(140), func(c *template.ColBuilder) {
        c.Text("FINAL",
            template.FontSize(72),
            template.TextColor(pdf.Gray(0.9)),
        )
    })
})

result, _ := doc.Save()

Flatten + Page Numbers

Flatten form fields and add page numbers to every page.

doc, _ := gpdf.Open(filledFormPDF)

// Flatten forms
doc.FlattenForms()

// Add page numbers
count, _ := doc.PageCount()
doc.EachPage(func(i int, p *template.PageBuilder) {
    p.Absolute(document.Mm(170), document.Mm(285), func(c *template.ColBuilder) {
        c.Text(fmt.Sprintf("%d / %d", i+1, count),
            template.FontSize(10),
            template.AlignRight(),
        )
    }, template.AbsoluteWidth(document.Mm(20)))
})

result, _ := doc.Save()

Safe Flatten (No Forms)

FlattenForms() is safe to call on any PDF — it's a no-op if no form fields exist.

// Works on any PDF, with or without forms
doc, _ := gpdf.Open(anyPDF)
doc.FlattenForms() // no-op if no AcroForm
result, _ := doc.Save()