Merge Two or More PDFs

import {PdfDocument} from "@ironsoftware/ironpdf";

(async () => {
    const html_a = `<p> [PDF_A] </p>
    <p> [PDF_A] 1st Page </p>
    <div style='page-break-after: always;'></div>
    <p> [PDF_A] 2nd Page</p>`;

    const html_b = `<p> [PDF_B] </p>
    <p> [PDF_B] 1st Page </p>
    <div style='page-break-after: always;'></div>
    <p> [PDF_B] 2nd Page</p>`;

    // Render HTML content to PDF documents
    const pdfdoc_a = await PdfDocument.fromHtml(html_a);
    const pdfdoc_b = await PdfDocument.fromHtml(html_b);

    // Merge the two PDF documents
    const merged = await PdfDocument.mergePdf([pdfdoc_a, pdfdoc_b]);

    // Save the merged PDF
    await merged.saveAs("Merged.pdf");  
})();

Merge Two or More PDFs

The code above enables you to combine multiple PDF documents created from different HTML contents into a single PDF file.

Two HTML contents have been rendered into separate PDF documents. The PdfDocument.mergePdf method is utilized to merge the two PDF documents, pdfdoc_a and pdfdoc_b, into a single PDF document named "merged."

The merging process is not limited to freshly rendered PDFs; it can also be applied to existing PDF documents using this method.

Explanation

Import: uses PdfDocument from the @ironsoftware/ironpdf package
Opening PDFs: PdfDocument.open(...) loads existing PDF files (rather than rendering HTML) — appropriate when merging pre‑existing PDFs.
Merging PDFs: PdfDocument.mergePdf([pdfA, pdfB]) combines the two documents into a single instance
Saving the result: merged.saveAs("merged.pdf") writes out the merged PDF, equivalent to Python’s merger.write(...)