Show when features are not fully supported

[manarchist8691]

It would be useful to have an optional “rendering diagnostics” mode that indicates when a PDF contains features that cannot be fully rendered by the viewer (e.g., unsupported objects, font substitution, rasterization fallback).
This could be implemented as:

A small, non-intrusive icon when such conditions occur
Hover/click reveals basic details (e.g., “Font substituted”, “Unsupported object ignored”)
Disabled by default to avoid impacting normal users

This would help users verify that what they are seeing matches the document’s intended content, especially in technical or engineering workflows.

The lack of such a feature has bitten me in the a** on multiple occasions. No viewer has this feature.

[GitHubRulesOK]

HMM Acrobat and other editing readers like Tracker Edge or SumatraPDF are supposed to follow the so called standards but even Adobe cant or won't do that as the point of all PDF etc renderings is to substitute fonts for numbers and if the numbers are poor make a best guess but that is the point of logging and that is a slow down to be kept minimal. So potentially possible but could swamp the device with poor file outputs. (many PDF if not most have failings)

Today I was appraised of an Adobe InDesign form (from a governmental site) that refused to work correctly in Acrobat so had to use Tracker to fix it as best I can to work in Adobe Software! So that's why I say most PDFs (the majority I see), are in some way "broken" and it may simply be the ones I am asked to correct!. Even those I write by hand will have some fail or another.