feat(render): add PDF renderer and tests (#4491)

* render: add PDF renderer and tests

* render: update PDF renderer copyright header

* test: add PDF rendering tests including 204 No Content in context_test.go

context.go

@@ -1224,6 +1224,12 @@ func (c *Context) XML(code int, obj any) {
 	c.Render(code, render.XML{Data: obj})
 }
 
+// PDF writes the given PDF binary data into the response body.
+// It also sets the Content-Type as "application/pdf".
+func (c *Context) PDF(code int, data []byte) {
+	c.Render(code, render.PDF{Data: data})
+}
+
 // YAML serializes the given struct as YAML into the response body.
 func (c *Context) YAML(code int, obj any) {
 	c.Render(code, render.YAML{Data: obj})

context_test.go

@@ -1320,6 +1320,33 @@ func TestContextRenderNoContentXML(t *testing.T) {
 	assert.Equal(t, "application/xml; charset=utf-8", w.Header().Get("Content-Type"))
 }
 
+// TestContextRenderPDF tests that the response is serialized as PDF
+// and Content-Type is set to application/pdf
+func TestContextRenderPDF(t *testing.T) {
+	w := httptest.NewRecorder()
+	c, _ := CreateTestContext(w)
+
+	data := []byte("%Test pdf content")
+	c.PDF(http.StatusCreated, data)
+
+	assert.Equal(t, http.StatusCreated, w.Code)
+	assert.Equal(t, data, w.Body.Bytes())
+	assert.Equal(t, "application/pdf", w.Header().Get("Content-Type"))
+}
+
+// Tests that no PDF is rendered if code is 204
+func TestContextRenderNoContentPDF(t *testing.T) {
+	w := httptest.NewRecorder()
+	c, _ := CreateTestContext(w)
+
+	data := []byte("%Test pdf content")
+	c.PDF(http.StatusNoContent, data)
+
+	assert.Equal(t, http.StatusNoContent, w.Code)
+	assert.Empty(t, w.Body.Bytes())
+	assert.Equal(t, "application/pdf", w.Header().Get("Content-Type"))
+}
+
 // TestContextRenderString tests that the response is returned
 // with Content-Type set to text/plain
 func TestContextRenderString(t *testing.T) {

render/pdf.go

@@ -0,0 +1,26 @@
+// Copyright 2026 Gin Core Team. All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+package render
+
+import "net/http"
+
+// PDF contains the given PDF binary data.
+type PDF struct {
+	Data []byte
+}
+
+var pdfContentType = []string{"application/pdf"}
+
+// Render (PDF) writes PDF data with custom ContentType.
+func (r PDF) Render(w http.ResponseWriter) error {
+	r.WriteContentType(w)
+	_, err := w.Write(r.Data)
+	return err
+}
+
+// WriteContentType (PDF) writes PDF ContentType for response.
+func (r PDF) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, pdfContentType)
+}

render/render.go

@@ -31,6 +31,7 @@ var (
 	_ Render     = (*AsciiJSON)(nil)
 	_ Render     = (*ProtoBuf)(nil)
 	_ Render     = (*TOML)(nil)
+	_ Render     = (*PDF)(nil)
 )
 
 func writeContentType(w http.ResponseWriter, value []string) {

render/render_test.go

@@ -466,6 +466,22 @@ func TestRenderXMLError(t *testing.T) {
 	assert.Contains(t, err.Error(), "xml: unsupported type: chan int")
 }
 
+func TestRenderPDF(t *testing.T) {
+	w := httptest.NewRecorder()
+	data := []byte("%Test pdf content")
+
+	pdf := PDF{data}
+
+	pdf.WriteContentType(w)
+	assert.Equal(t, "application/pdf", w.Header().Get("Content-Type"))
+
+	err := pdf.Render(w)
+	require.NoError(t, err)
+
+	assert.Equal(t, data, w.Body.Bytes())
+	assert.Equal(t, "application/pdf", w.Header().Get("Content-Type"))
+}
+
 func TestRenderRedirect(t *testing.T) {
 	req, err := http.NewRequest(http.MethodGet, "/test-redirect", nil)
 	require.NoError(t, err)