Whenever possible, add accessible features when you create the PDF so you have access to the document structure. Even if the output from an authoring application is not entirely PDF/UA compliant, it can add tags more effectively.
Non-tagged PDF processing
If PDF is not-tagged, PDFix attempts to automatically tag it using the Accessibility->Autotag action. PDFix utilizes a document layout recognition algorithm to identify hierarchical structure and establish the reading order of elements. The accuracy of the detected tag structure relies on the complexity of the document layout. To enhance this quality, navigate to 
Template side panel.
Two automated options are available for adding a new structure to PDFs:
Autotag
- Select Template you want to use for autotag. If empty, document current template is used
- Check Preflight if you want to run automatic headers, footers and heading detection
- Check Add Layout Attribute to to automatically populate all identified layout attributes into tags
- Check Sequential Heading Levels to keep headings in sequentially-descending order
Make Accessible
Make Accessible is one of the Default actions that not only creates a tag tree but also runs all neccessary steps to make PDF accessible.
Make Accessible is created as a pipeline of individual actions. To set desired parameters, please review each individual actions.
Processing of Tagged PDF
If your PDF already contains tags, PDFix provides numerous tools to address most accessibility issues.
To ensure if your PDF is fully compliant, begin by running the Validation first.
Depending on the type of validation error, PDFix offers various options to fix it, including automated, semi-automated, and manual too.
Automated & Semi automated fixes
PDFix provides high-level actions capable of automatically resolving the most common accessibility issues. These actions can be applied either to the entire document or to specific selections.
Manual fixes
In the document view you can navigate to appropriate side panels to manually edit PDF structures.
