1. I set the background color of your document in the Document-General section of Doc Customizer, then Clear it, and the document is displayed now with white background (so the black background is eliminated).
However if I set any background color, it will be black on your site. this problem does not occur on our test sites, so it may be a theme or plugin conflict. Try to find it using the method that I suggested on the other post.
2. There is a problem with the Chinese fonts, when you create PDF documents.
There is a workaround: if you set HTML format in the Document tab / Sales Order (or other doc type) sub-tab, then Chinese fonts are displayed without problem.
If we are in pdf mode, the problem with the font setting is similar to the background setting. On our test sites, we can set any fonts without problem, but on your site if I change the found, it has no effect. The font can be set in Font Family filed of the Document-General tab of Doc Customizer.
Please check that if you set a special font, it is appear on the document, when you are looking for the plugin conflicts.
You can use any font, that is supports Chinese characters.
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