fix: pdf/a compliance of attachments

lib/mixins/attachments.js

@@ -12,10 +12,12 @@ export default {
    *  * options.hidden: if true, do not add attachment to EmbeddedFiles dictionary. Useful for file attachment annotations
    *  * options.creationDate: override creation date
    *  * options.modifiedDate: override modified date
+   *  * options.relationship: Relationship between the PDF document and its attached file. Can be 'Alternative', 'Data', 'Source', 'Supplement' or 'Unspecified'.
    * @returns filespec reference
    */
   file(src, options = {}) {
     options.name = options.name || src;
+    options.relationship = options.relationship || 'Unspecified';
 
     const refBody = {
       Type: 'EmbeddedFile',
@@ -85,6 +87,7 @@ export default {
     // add filespec for embedded file
     const fileSpecBody = {
       Type: 'Filespec',
+      AFRelationship: options.relationship,
       F: new String(options.name),
       EF: { F: ref },
       UF: new String(options.name)
@@ -99,6 +102,13 @@ export default {
       this.addNamedEmbeddedFile(options.name, filespec);
     }
 
+    // Add file to the catalogue to be PDF/A3 compliant
+    if (this._root.data.AF) {
+      this._root.data.AF.push(filespec);
+    } else {
+      this._root.data.AF = [filespec];
+    }
+
     return filespec;
   }
 };