Got it, let's break down how to fix your PDF merging issue. You're dealing with two PDFs—one is 1.4 with a trailer, the other is a 1.5 version from Google Docs without a trailer, and your current merge script can't handle the latter. Here are two solid approaches:

Option 1: Export Google Docs as PDF 1.4 Version #

The default getAs('application/pdf') method exports Google Docs to PDF 1.5, but you can force a 1.4 export by using Google Docs' direct export URL with the pdfVersion parameter. Here's a script to do that:

function exportGDocToPDF1_4(docId) {
  // Build the export URL with PDF 1.4 specification
  const exportUrl = `https://docs.google.com/document/d/${docId}/export?format=pdf&pdfVersion=1.4`;
  // Get OAuth token for authentication
  const authToken = ScriptApp.getOAuthToken();
  
  // Fetch the PDF blob
  const response = UrlFetchApp.fetch(exportUrl, {
    headers: { 'Authorization': `Bearer ${authToken}` }
  });
  
  // Create the PDF file in Drive
  const pdfBlob = response.getBlob().setName('TEST pdf (1.4)');
  const pdfFile = DriveApp.createFile(pdfBlob);
  
  return pdfFile.getId();
}

Just replace docId with your Google Document ID, and this will generate a PDF 1.4 version with the proper trailer, which should work with your existing merge script.

Option 2: Use PDF-Lib for Robust PDF Merging #

If you don't want to mess with PDF versions, PDF-Lib is a powerful JavaScript library that can merge PDFs regardless of their version or trailer status. Here's how to implement it in Apps Script:

Step 1: Add PDF-Lib to Your Project #

1. Go to the PDF-Lib GitHub repo, download the latest pdf-lib.min.js from the dist folder.
2. In your Apps Script editor, create a new file (click + > Script), name it pdf-lib, and paste the entire contents of pdf-lib.min.js into it.

Step 2: Merging Script #

async function mergeTwoPDFs(fileId1, fileId2) {
  // Access PDF-Lib's core functionality
  const { PDFDocument } = PDFLib;

  // Fetch the two PDF files from Drive as blobs
  const pdf1Blob = DriveApp.getFileById(fileId1).getBlob();
  const pdf2Blob = DriveApp.getFileById(fileId2).getBlob();

  // Convert blobs to Uint8Arrays (required by PDF-Lib)
  const pdf1Bytes = new Uint8Array(pdf1Blob.getBytes());
  const pdf2Bytes = new Uint8Array(pdf2Blob.getBytes());

  // Create a new empty PDF document for merging
  const mergedPdfDoc = await PDFDocument.create();

  // Load and copy pages from the first PDF
  const pdf1Doc = await PDFDocument.load(pdf1Bytes);
  const pdf1Pages = await mergedPdfDoc.copyPages(pdf1Doc, pdf1Doc.getPageIndices());
  pdf1Pages.forEach(page => mergedPdfDoc.addPage(page));

  // Load and copy pages from the second PDF
  const pdf2Doc = await PDFDocument.load(pdf2Bytes);
  const pdf2Pages = await mergedPdfDoc.copyPages(pdf2Doc, pdf2Doc.getPageIndices());
  pdf2Pages.forEach(page => mergedPdfDoc.addPage(page));

  // Save the merged PDF as a blob
  const mergedPdfBytes = await mergedPdfDoc.save();
  const mergedBlob = Utilities.newBlob(mergedPdfBytes, 'application/pdf', 'Merged Result.pdf');

  // Create the merged file in Drive and return its ID
  const mergedFile = DriveApp.createFile(mergedBlob);
  return mergedFile.getId();
}

This script parses the structure of each PDF directly, so it doesn't care about trailers or version differences—it just copies all pages into a new merged PDF.

Which Option to Choose? #

• If you need to stick with your existing merge script, go with Option 1 to generate the 1.4 PDF.
• If you want a more future-proof solution that works with any PDF version, Option 2 with PDF-Lib is better—it handles edge cases way more reliably.

内容的提问来源于stack exchange，提问作者JingleBells