Document cannot be saved, please check your permissions.

Describe the bug
Exporting a .docx document to PDF fails

To Reproduce

1. Editing a text document in the web-interface
2. choosing "Export As"
3. "PDF Document"
4. "Save As" (I choose path + filename)
5. "PDF Options" (I click Export)

I get the error:
Document cannot be saved, please check your permissions.

I can save the document as .docx under a new name in the same folder, so permissions don't seem directly to be the issue.

Expected behavior
I want the pdf file to be generated in the selected directory.

Screenshots

Client details:

• OS: Ubuntu
• Browser Chromium and Firefox tested

Server details

I have just installed the apps from the admin web interface, so I don't think there are any non-standard settings.

Debian
Web server: Apache

Database: mysql, Version: 10.11.14

PHP version: Version: 8.2.29

Nextcloud version: Nextcloud Hub 25 Autumn (32.0.2)

Version of the richdocuments app Nextcloud Office Version 9.0.2

Version of Collabora Online Collabora Online - Built-in CODE Server
Version 25.4.702

Configuration of the richdocuments app

occ config:list richdocuments
{
    "apps": {
        "richdocuments": {
            "canonical_webroot": "",
            "disable_certificate_verification": "yes",
            "doc_format": "ooxml",
            "enabled": "yes",
            "external_apps": "",
            "installed_version": "9.0.2",
            "public_wopi_url": "https:\/\/DOMAIN",
            "types": "filesystem,prevent_group_restriction",
            "wopi_allowlist": "",
            "wopi_url": "https:\/\/DOMAIN\/apps\/richdocumentscode\/proxy.php?req="
        }
    }
}

Start by reproducing the .docx-to-PDF export flow in the web interface using the reported Ubuntu, Apache, MySQL, PHP, Nextcloud, richdocuments, and built-in CODE versions. Inspect the richdocuments configuration and export path to determine why PDF output fails despite saving .docx successfully. Done means a PDF is generated in the selected directory without the permissions error.