使用PDFBox 2.0.17嵌入的PDF附件无法在Adobe Reader打开求助

I’ve dealt with similar cross-viewer attachment compatibility headaches using PDFBox before, so let’s walk through what’s likely causing this and how to fix it.

Possible Reasons for the Issue #

• Strict Adobe Metadata Requirements: Adobe Reader is pickier about attachment metadata than browsers like Firefox. If your code skips critical entries like the AFRelationship key or uses incorrect MIME type formatting, Adobe might refuse to recognize the embedded PDFs as valid.
• PDFBox 2.0.17 Bug: Older versions of PDFBox had known quirks handling PDFs with non-standard compression or cross-reference structures. Your problematic files (10.pdf, 11.pdf, 12.pdf) might have traits that trigger this bug specifically in 2.0.17.
• Missing File Spec Entries: Adobe requires specific dictionary entries (like F for filename and UF for Unicode filename) to process attachments. If these are missing or malformed, Reader will fail to open the files.

Step-by-Step Fixes #

1. Fix Attachment Metadata in Your Code
   Make sure you’re explicitly setting all required metadata when adding attachments. Here’s an adjusted code snippet to align with Adobe’s expectations:

   PDDocument mainDoc = new PDDocument();
   mainDoc.addPage(new PDPage());
   
   // Process a problematic attachment (e.g., 10.pdf)
   PDFileSpecification fileSpec = PDFileSpecification.createEmbeddedFile(mainDoc, new File("10.pdf"));
   fileSpec.setFile("10.pdf");
   fileSpec.setUnicodeFile("10.pdf");
   fileSpec.setMIMEType("application/pdf");
   // Critical: Set AFRelationship to tell Adobe this is a data attachment
   fileSpec.getCOSObject().setName("AFRelationship", "Data");
   
   PDAttachment attachment = new PDAttachment();
   attachment.setFile(fileSpec);
   attachment.setName("10.pdf");
   attachment.setDescription("Embedded PDF document");
   
   mainDoc.getDocumentCatalog().getNames().getEmbeddedFiles().add(attachment);
   
   mainDoc.save("fixed_attachments.pdf");
   mainDoc.close();
   

   The key addition here is the AFRelationship entry—this is often the missing piece for Adobe Reader compatibility.

2. Upgrade PDFBox to the Latest Stable Version
   Version 2.0.17 is several years old, and many file-embedding bugs have been patched in newer releases (as of now, the latest stable is 2.0.32). Upgrading your dependency might resolve the issue outright without code changes.

3. Normalize Problematic PDFs First
   Some PDFs have non-standard structures that confuse older PDFBox versions. Try re-saving 10.pdf, 11.pdf, and 12.pdf using Adobe Reader itself (File > Save As > PDF) to normalize their formatting before embedding. This often fixes compatibility gaps.

4. Check for Encryption or Restrictions
   If the problematic PDFs are encrypted or have editing restrictions, Adobe Reader might block them as attachments even if Firefox ignores these restrictions. Use this quick check with PDFBox:

   PDDocument testDoc = PDDocument.load(new File("10.pdf"));
   System.out.println("Is encrypted? " + testDoc.isEncrypted());
   testDoc.close();
   

   If encrypted, decrypt the files using PDFBox’s decryption tools before embedding them.

Verify the Fix #

After applying these changes, inspect the embedded metadata to confirm everything is set correctly:

PDDocument outputDoc = PDDocument.load(new File("fixed_attachments.pdf"));
PDEmbeddedFilesNameTreeNode embeddedFiles = outputDoc.getDocumentCatalog().getNames().getEmbeddedFiles();
for (COSName name : embeddedFiles.getNames().keySet()) {
    PDFileSpecification spec = embeddedFiles.getNames().get(name);
    System.out.println("Attachment Name: " + spec.getFile());
    System.out.println("MIME Type: " + spec.getMIMEType());
    System.out.println("AFRelationship: " + spec.getCOSObject().getString("AFRelationship"));
}
outputDoc.close();

This will help you confirm that all required metadata is present for Adobe Reader to recognize the attachments.

内容的提问来源于stack exchange，提问作者D Vekaria