Tagging Evaluation

What are XObjects?

XObjects in PDFs are reusable graphical objects that allow for efficient rendering and storage. They include Form XObjects (vector graphics, text, or images) and Image XObjects (bitmap images). XObjects are defined once and can be referenced multiple times within the PDF, reducing file size and ensuring consistent visual representation. They are particularly useful for complex layouts, repeating elements, and incorporating external content.

When creating an accessible document, XObjects can present significant challenges, as the content within them is often grouped together as a single element, making tagging difficult. Below are some solutions to address these issues:

How to tag xObject figures & images

Tagging xObject elements can cause multiple issues such as Syntax errors, visual erros or PAC issues. To avoid those kind of problems some work can be done inside the content panel.

1. Identify the Relevant xObject
   • Locate the xObject element that’s causing issues. It’s important to isolate the specific item to avoid unintended changes to other parts of the PDF.
2. Wrap the xObject in an "Artifact" Tag
   • Create an Artifact container to safely isolate the xObject:
     • Right-click on any tag in the Tags panel
       • Select New Container & Enter "Artifact" as the tag type
       • Note: The new Artifact tag will initially appear as a child of the tag you clicked. Drag it out to a suitable position in the tag tree.
       • Then, move the identified xObject element into the newly created Artifact tag.
3. Tag or Remove the Element as Needed
   • Tag it as needed
   • Or delete it directly from the Tags panel

It should look like this

Note :

1. Always make sure that the integrity of the document is intact.
2. This method might not work for text or table elements. For those types of elements the methods bellow would be more efficient.
3. Always check PAC when editing xObjects as they are very specific and volatile.

How to correct.

Converting the document using Distiller

One effective method to address issues with XObjects is to use the distillation process for the PDF. This approach flattens the document's content, ensuring that each element is represented individually rather than being grouped together.

1. Export the Document to PostScript
   • Open your PDF document in Adobe Acrobat.
2. Export to PostScript
   • Select File > Export To > PostScript.
   • Choose a location to save the PostScript (.ps) file.
   • Save the file with a .ps extension.
3. Launch Acrobat Distiller
4. Set Preferences
   • In Acrobat Distiller, go to Edit > Preferences
   • Under Adobe PDF Settings, ensure that Embed Fonts is enabled. This ensures that fonts are embedded into the PDF during the conversion process.
   • Choose an appropriate Job Option like High Quality Print or Press Quality, depending on the desired output quality.
5. Add the PostScript File
   • Drag and drop the PostScript (.ps) file you saved earlier into the Acrobat Distiller window, or use File > Open to locate and select the file.
6. Verify XObject Fixes
   • Open the newly created PDF in Adobe Acrobat Pro.
   • Check the document to confirm whether the XObjects have been successfully removed.

Additional Tips

• While this method is an effective way to remove XObjects, it can also have potential drawbacks, particularly affecting the document's visual appearance. Therefore, it is essential to thoroughly review the document to ensure it remains visually intact after processing.
• While distilling a document is highly effective, it can also introduce multiple font encoding issues. When evaluating this method's effectiveness, consider that character encoding can be corrected, but the process should not be overly time-consuming. If there are too many errors requiring extensive manual fixes, it may be more efficient to explore alternative solutions for resolving XObject errors.

Cut and Copy Method

This method involves extracting and reapplying the content contained within the XObject.

Step 1: Open the PDF in Adobe Acrobat Pro

• Launch Adobe Acrobat Pro.
• Open the PDF containing the XObject issues.

Step 2: Select the XObject

• Go to the Edit tool in the toolbar or use the Edit PDF option from the tools panel.
• Click on the XObject or the content you suspect is grouped as an XObject.

Step 3: Cut the XObject

• Right-click on the selected content and choose Cut from the context menu. Alternatively, press Ctrl+X (Windows) or Command+X (Mac).
• The XObject will be removed temporarily and stored in the clipboard.

Step 4: Paste the Content Back

• Right-click in the same location where the XObject was removed and select Paste. Alternatively, press Ctrl+V (Windows) or Command+V (Mac).
• This action reinserts the content as an editable and taggable object rather than a grouped XObject.

Step 5: Verify the Content

• Check the document to ensure the pasted content appears correctly and remains visually intact.
• Use the Accessibility tools in Acrobat to confirm that the content is now selectable and can be tagged properly.

Step 6: Repeat for Other XObjects

• If the document contains multiple XObjects, repeat the process for each problematic element.

Additional Tips

• Always create a backup copy of your original PDF before making changes, as this method alters the structure of the document.
• When pasting the content back into the document, use Acrobat's alignment tools to ensure the content is placed precisely where it was originally.
• After pasting, verify that the new content does not overlap with other elements or cause layout issues.
• Use Acrobat’s Accessibility Check tool to confirm that the newly added content is now taggable and accessible.
• For XObjects containing grouped images or complex layouts, consider breaking them down into smaller sections before reapplying.
• Copy-pasting multiple times may degrade image quality or disrupt formatting. Try to minimize repeated actions.
• If working with a large document, focus on one page or section at a time to maintain control and avoid mistakes.
• After reapplying text content, ensure it is selectable and encoded properly for accessibility purposes.
• Once all changes are made, review the entire document for any unintended visual or structural issues.