diff --git a/src/__tests__/pdf-options-builder.test.ts b/src/__tests__/pdf-options-builder.test.ts
new file mode 100644
index 0000000..30641aa
--- /dev/null
+++ b/src/__tests__/pdf-options-builder.test.ts
@@ -0,0 +1,68 @@
+import { describe, it, expect } from "vitest";
+import { buildPdfOptions, PdfRenderOptions } from "../services/browser.js";
+
+describe("buildPdfOptions", () => {
+  it("returns sensible defaults when no options given", () => {
+    const result = buildPdfOptions({});
+    expect(result).toEqual({
+      format: "A4",
+      landscape: false,
+      printBackground: true,
+      margin: { top: "0", right: "0", bottom: "0", left: "0" },
+    });
+  });
+
+  it("passes through all provided options", () => {
+    const opts: PdfRenderOptions = {
+      format: "Letter",
+      landscape: true,
+      printBackground: false,
+      margin: { top: "10mm", bottom: "10mm" },
+      scale: 1.5,
+      pageRanges: "1-3",
+      preferCSSPageSize: true,
+      width: "210mm",
+      height: "297mm",
+      headerTemplate: "<span>Header</span>",
+      footerTemplate: "<span>Footer</span>",
+      displayHeaderFooter: true,
+    };
+    const result = buildPdfOptions(opts);
+    expect(result.format).toBe("Letter");
+    expect(result.landscape).toBe(true);
+    expect(result.printBackground).toBe(false);
+    expect(result.margin).toEqual({ top: "10mm", bottom: "10mm" });
+    expect(result.scale).toBe(1.5);
+    expect(result.pageRanges).toBe("1-3");
+    expect(result.preferCSSPageSize).toBe(true);
+    expect(result.width).toBe("210mm");
+    expect(result.height).toBe("297mm");
+    expect(result.headerTemplate).toBe("<span>Header</span>");
+    expect(result.footerTemplate).toBe("<span>Footer</span>");
+    expect(result.displayHeaderFooter).toBe(true);
+  });
+
+  it("omits undefined optional fields from output", () => {
+    const result = buildPdfOptions({ format: "A4" });
+    expect(result).not.toHaveProperty("scale");
+    expect(result).not.toHaveProperty("pageRanges");
+    expect(result).not.toHaveProperty("preferCSSPageSize");
+    expect(result).not.toHaveProperty("width");
+    expect(result).not.toHaveProperty("height");
+    expect(result).not.toHaveProperty("headerTemplate");
+    expect(result).not.toHaveProperty("footerTemplate");
+  });
+
+  it("handles printBackground false explicitly", () => {
+    const result = buildPdfOptions({ printBackground: false });
+    expect(result.printBackground).toBe(false);
+  });
+
+  it("defaults displayHeaderFooter to false only when explicitly set", () => {
+    const r1 = buildPdfOptions({});
+    expect(r1).not.toHaveProperty("displayHeaderFooter");
+
+    const r2 = buildPdfOptions({ displayHeaderFooter: false });
+    expect(r2.displayHeaderFooter).toBe(false);
+  });
+});
diff --git a/src/__tests__/setup.ts b/src/__tests__/setup.ts
index 543b715..8bfbc29 100644
--- a/src/__tests__/setup.ts
+++ b/src/__tests__/setup.ts
@@ -53,7 +53,10 @@ vi.mock("../services/keys.js", () => {
 });
 
 // Mock browser service
-vi.mock("../services/browser.js", () => ({
+vi.mock("../services/browser.js", async (importOriginal) => {
+  const actual = await importOriginal<Record<string, unknown>>();
+  return {
+  buildPdfOptions: actual.buildPdfOptions,
   initBrowser: vi.fn().mockResolvedValue(undefined),
   closeBrowser: vi.fn().mockResolvedValue(undefined),
   renderPdf: vi.fn().mockResolvedValue({ pdf: Buffer.from("%PDF-1.4 mock pdf content here"), durationMs: 10 }),
@@ -68,7 +71,8 @@ vi.mock("../services/browser.js", () => ({
     uptimeMs: 10000,
     browsers: [],
   }),
-}));
+};
+});
 
 // Mock verification service
 vi.mock("../services/verification.js", () => ({
diff --git a/src/services/browser.ts b/src/services/browser.ts
index 0263cfb..41d4622 100644
--- a/src/services/browser.ts
+++ b/src/services/browser.ts
@@ -221,7 +221,7 @@ export async function closeBrowser(): Promise<void> {
   instances.length = 0;
 }
 
-import type { PaperFormat, PuppeteerLifeCycleEvent } from "puppeteer";
+import type { PaperFormat, PDFOptions, PuppeteerLifeCycleEvent } from "puppeteer";
 
 export interface PdfRenderOptions {
   format?: PaperFormat;
@@ -238,6 +238,27 @@ export interface PdfRenderOptions {
   height?: string;
 }
 
+/** Build a Puppeteer-compatible PDFOptions object from user-supplied render options. */
+export function buildPdfOptions(options: PdfRenderOptions): Record<string, unknown> {
+  const result: Record<string, unknown> = {
+    format: options.format || "A4",
+    landscape: options.landscape || false,
+    printBackground: options.printBackground !== false,
+    margin: options.margin || { top: "0", right: "0", bottom: "0", left: "0" },
+  };
+
+  if (options.headerTemplate !== undefined) result.headerTemplate = options.headerTemplate;
+  if (options.footerTemplate !== undefined) result.footerTemplate = options.footerTemplate;
+  if (options.displayHeaderFooter !== undefined) result.displayHeaderFooter = options.displayHeaderFooter;
+  if (options.scale !== undefined) result.scale = options.scale;
+  if (options.pageRanges) result.pageRanges = options.pageRanges;
+  if (options.preferCSSPageSize !== undefined) result.preferCSSPageSize = options.preferCSSPageSize;
+  if (options.width) result.width = options.width;
+  if (options.height) result.height = options.height;
+
+  return result;
+}
+
 export async function renderPdf(
   html: string,
   options: PdfRenderOptions = {}
@@ -251,20 +272,7 @@ export async function renderPdf(
       (async () => {
         await page.setContent(html, { waitUntil: "domcontentloaded", timeout: 15_000 });
         await page.addStyleTag({ content: "* { margin: 0; padding: 0; } body { margin: 0; }" });
-        const pdf = await page.pdf({
-          format: options.format || "A4",
-          landscape: options.landscape || false,
-          printBackground: options.printBackground !== false,
-          margin: options.margin || { top: "0", right: "0", bottom: "0", left: "0" },
-          headerTemplate: options.headerTemplate,
-          footerTemplate: options.footerTemplate,
-          displayHeaderFooter: options.displayHeaderFooter || false,
-          ...(options.scale !== undefined && { scale: options.scale }),
-          ...(options.pageRanges && { pageRanges: options.pageRanges }),
-          ...(options.preferCSSPageSize !== undefined && { preferCSSPageSize: options.preferCSSPageSize }),
-          ...(options.width && { width: options.width }),
-          ...(options.height && { height: options.height }),
-        });
+        const pdf = await page.pdf(buildPdfOptions(options) as Parameters<Page["pdf"]>[0]);
         return Buffer.from(pdf);
       })(),
       new Promise<never>((_, reject) => {
@@ -330,20 +338,7 @@ export async function renderUrlPdf(
           waitUntil: options.waitUntil || "domcontentloaded",
           timeout: 30_000,
         });
-        const pdf = await page.pdf({
-          format: options.format || "A4",
-          landscape: options.landscape || false,
-          printBackground: options.printBackground !== false,
-          margin: options.margin || { top: "0", right: "0", bottom: "0", left: "0" },
-          ...(options.headerTemplate && { headerTemplate: options.headerTemplate }),
-          ...(options.footerTemplate && { footerTemplate: options.footerTemplate }),
-          ...(options.displayHeaderFooter !== undefined && { displayHeaderFooter: options.displayHeaderFooter }),
-          ...(options.scale !== undefined && { scale: options.scale }),
-          ...(options.pageRanges && { pageRanges: options.pageRanges }),
-          ...(options.preferCSSPageSize !== undefined && { preferCSSPageSize: options.preferCSSPageSize }),
-          ...(options.width && { width: options.width }),
-          ...(options.height && { height: options.height }),
-        });
+        const pdf = await page.pdf(buildPdfOptions(options) as Parameters<Page["pdf"]>[0]);
         return Buffer.from(pdf);
       })(),
       new Promise<never>((_, reject) => {