generate the document ID on-demand and not in the class constructor

packages/pdfkit/src/document.js

@@ -115,9 +115,6 @@ class PDFDocument extends stream.Readable {
       });
     }
 
-    // Generate file ID
-    this._id = PDFSecurity.generateFileID(this.info);
-
     // Initialize security settings
     // this._security = PDFSecurity.create(this, options);
 
@@ -133,6 +130,10 @@ class PDFDocument extends stream.Readable {
     }
   }
 
+  _id() {
+    return PDFSecurity.generateFileID(this.info);
+  }
+
   addPage(options) {
     // end the current page if needed
     if (options == null) {
@@ -300,11 +301,12 @@ class PDFDocument extends stream.Readable {
     }
 
     // trailer
+    const id = this._id();
     const trailer = {
       Size: this._offsets.length + 1,
       Root: this._root,
       Info: this._info,
-      ID: [this._id, this._id]
+      ID: [id, id]
     };
 
     // if (this._security) {