This patch makes the "/ID" field optional.

If the environment variable GS_GENERATE_UUIDS is set to "0" or "no", it will
not write out the "/ID" field (if that's permissible).

Upstream does not want to do this.

See: https://bugs.ghostscript.com/show_bug.cgi?id=698208
diff -ur orig/gnu-ghostscript-9.14.0/devices/vector/gdevpdf.c gnu-ghostscript-9.14.0/devices/vector/gdevpdf.c
--- orig/gnu-ghostscript-9.14.0/devices/vector/gdevpdf.c	2017-07-09 23:30:28.960479189 +0200
+++ gnu-ghostscript-9.14.0/devices/vector/gdevpdf.c	2017-07-09 23:34:34.306524488 +0200
@@ -1810,8 +1810,11 @@
      * +1 for the linearisation dict and +1 for the primary hint stream.
      */
     linear_params->FirsttrailerOffset = gp_ftell(linear_params->Lin_File.file);
-    gs_sprintf(LDict, "\ntrailer\n<</Size %ld/Info %d 0 R/Root %d 0 R/ID[%s%s]/Prev %d>>\nstartxref\r\n0\n%%%%EOF\n        \n",
-        linear_params->LastResource + 3, pdev->ResourceUsage[linear_params->Info_id].NewObjectNumber, pdev->ResourceUsage[linear_params->Catalog_id].NewObjectNumber, fileID, fileID, 0);
+    gs_sprintf(LDict, "\ntrailer\n<</Size %ld/Info %d 0 R/Root %d 0 R",
+        linear_params->LastResource + 3, pdev->ResourceUsage[linear_params->Info_id].NewObjectNumber, pdev->ResourceUsage[linear_params->Catalog_id].NewObjectNumber);
+    if (pdev->OwnerPassword.size > 0 || !(!getenv("GS_GENERATE_UUIDS") || (strcasecmp(getenv("GS_GENERATE_UUIDS"), "0") != 0 && strcasecmp(getenv("GS_GENERATE_UUIDS"), "no") != 0))) /* ID is mandatory when encrypting */
+        gs_sprintf(LDict, "/ID[%s%s]", fileID, fileID);
+    gs_sprintf(LDict, "/Prev %d>>\nstartxref\r\n0\n%%%%EOF\n        \n", 0);
     gp_fwrite(LDict, strlen(LDict), 1, linear_params->Lin_File.file);
 
     /* Write document catalog (Part 4) */
@@ -2346,8 +2349,11 @@
     if (code != 0)
         return_error(gs_error_ioerror);
 
-    gs_sprintf(LDict, "\ntrailer\n<</Size %ld/Info %d 0 R/Root %d 0 R/ID[%s%s]/Prev %"PRId64">>\nstartxref\r\n0\n%%%%EOF\n",
-        linear_params->LastResource + 3, pdev->ResourceUsage[linear_params->Info_id].NewObjectNumber, pdev->ResourceUsage[linear_params->Catalog_id].NewObjectNumber, fileID, fileID, mainxref);
+    gs_sprintf(LDict, "\ntrailer\n<</Size %ld/Info %d 0 R/Root %d 0 R",
+        linear_params->LastResource + 3, pdev->ResourceUsage[linear_params->Info_id].NewObjectNumber, pdev->ResourceUsage[linear_params->Catalog_id].NewObjectNumber);
+    if (pdev->OwnerPassword.size > 0 || !(!getenv("GS_GENERATE_UUIDS") || (strcasecmp(getenv("GS_GENERATE_UUIDS"), "0") != 0 || strcasecmp(getenv("GS_GENERATE_UUIDS"), "no") != 0))) /* ID is mandatory when encrypting */
+        gs_sprintf(LDict, "/ID[%s%s]", fileID, fileID);
+    gs_sprintf(LDict, "/Prev %"PRId64">>\nstartxref\r\n0\n%%%%EOF\n", mainxref);
     gp_fwrite(LDict, strlen(LDict), 1, linear_params->sfile);
 
     code = gp_fseek(linear_params->sfile, pdev->ResourceUsage[HintStreamObj].LinearisedOffset, SEEK_SET);
@@ -3012,10 +3018,12 @@
             stream_puts(s, "trailer\n");
             pprintld3(s, "<< /Size %ld /Root %ld 0 R /Info %ld 0 R\n",
                   pdev->next_id, Catalog_id, Info_id);
-            stream_puts(s, "/ID [");
-            psdf_write_string(pdev->strm, pdev->fileID, sizeof(pdev->fileID), 0);
-            psdf_write_string(pdev->strm, pdev->fileID, sizeof(pdev->fileID), 0);
-            stream_puts(s, "]\n");
+            if (pdev->OwnerPassword.size > 0 || !(!getenv("GS_GENERATE_UUIDS") || (strcasecmp(getenv("GS_GENERATE_UUIDS"), "0") != 0 || strcasecmp(getenv("GS_GENERATE_UUIDS"), "no") != 0))) { /* ID is mandatory when encrypting */
+                stream_puts(s, "/ID [");
+                psdf_write_string(pdev->strm, pdev->fileID, sizeof(pdev->fileID), 0);
+                psdf_write_string(pdev->strm, pdev->fileID, sizeof(pdev->fileID), 0);
+                stream_puts(s, "]\n");
+            }
             if (pdev->OwnerPassword.size > 0) {
                 pprintld1(s, "/Encrypt %ld 0 R ", Encrypt_id);
             }