RT#7896: FR: Enhance link border color handling

[rakunavi]

Hello all,

This is a feature enhancement and UI refinement proposal regarding how the UI (Properties pane / Format tab) and saving engine handle Link annotations that do not contain an explicit /C (Color) entry in their dictionary.

Background & Observation
According to ISO 32000-1:2008, when the /C entry is absent, the color is device-dependent (falling back to black in most standard viewers). Adobe Acrobat utilizes this specification as a file-size optimization technique; when a user sets a link border color to black and the width to 0 pt, Acrobat strips the /C entry entirely from the output file to minimize file size. This optimized structure is widely seen in many publicly distributed PDFs, including PDF-XChange Editor's own official manuals.

When PDF-XChange Editor opens such files, the rendering engine correctly follows the ISO fallback rule and renders the border as black when the width is increased. However, the UI and the saving logic show room for improvement:

1. Current UI Behavior:
   When the border width is increased from 0 pt to 1 pt, a black border appears on the page, but the UI continues to display Stroke Color: None, creating a minor visual mismatch for general users.
2. Comparison with Competitors:
   While Foxit PDF Editor fails to render the fallback border entirely, PDF-XChange Editor's rendering engine is far superior in terms of ISO compliance. However, the UI display could be more intuitive.

Steps to Reproduce

1. Open the official PDF-XChange Editor manual (PDFXE11_MAN.pdf) provided on your website.
2. Select any standard link annotation inside your manual (e.g., the links on page 3), which naturally lacks a /C entry due to optimized industry standards.
3. Observe the UI: Border Width: 0 pt and Stroke Color: None.
   figure1.png
4. Increase the Border Width to 1 pt.
   figure2.png

Proposed Solution for the Ultimate UX
To make PDF-XChange Editor surpass Acrobat's implementation in both data optimization and user friendliness, I propose the following two-fold approach:

1. Refining the UI (Placeholder Display):
   When the /C entry is absent in the input file, instead of displaying a flat "None", the UI could display a placeholder like "None (Default: Black)" or "Black (Auto)" in muted/gray text. This accurately informs general users of the expected color outcome while maintaining technical accuracy for power users.
2. Implementing Auto-Optimization on Save:
   When a user creates or modifies a Link annotation to a solid black color with a 0-pt width within PDF-XChange Editor, the saving engine could automatically omit the /C entry to optimize the final file size, just as Acrobat does.

By combining Acrobat’s smart data-stripping optimization with a more informative and helpful UI display (e.g., "Black (Auto)"), PDF-XChange Editor can achieve the most sophisticated and complete implementation in the PDF software industry.

Thank you for taking the time to read this message.

Best regards,
rakunavi

- PDF-XChange Editor PRO Version: 11.0.1
- OS Version: Windows 11 Pro / Home 25H2 Build 26200.8655
- PC Model: GMKtec Nucbox M7 Pro with HUION Kamvas Pro 19 / Lenovo IdeaPad C340-15IWL

[EDIT] Since a ticket has been officially issued for this request, I have changed the topic title as follows. 2026-7-25 15:19 JST (UTC+9)

• Previous Title: UI/UX FR: Handling of missing /C entry in Link annotations (Acrobat-style file optimization and "Black (Auto)" display)
• New Title: RT#7896: FR: Enhance link border color handling

[Daniel - PDF-XChange]

Hello, rakunavi

Thank you for the suggestion, and sorry for the long delay on a response. This has been passed along to the Dev team for consideration.

RT#7896: FR: Enhance link border color handling

Kind regards,

[rakunavi]

Thank you, Daniel, for creating the ticket!

Thank you for taking time out of your busy schedule.
Please give my best regards to developers.

Best regards,
rakunavi

[Daniel - PDF-XChange]