Acrobat Reader showing Chinese as bracket when try to comment in the file

Hi Lingshan

Hope you are doing well and sorry for the trouble. As described the the text entered shows as little boxes.

It seems to be a font issue as the fonts are not properly embedded into the PDF file when it was created. Please try the following steps and see if that helps: Go to Edit (Windows), Adobe Acrobat (Mac) > Preferences > Page Display > Rendering > Select 'Use Local Fonts' > Click OK

To embed fonts in a PDF, the ideal method is to embed them when the PDF is made (ie, saved as a PDF or exported to PDF) from the source document (ie, Word, PowerPoint, Adobe InDesign, etc.). Look at the conversion options, settings, or preferences to set the conversion to embed the fonts.

If you're dealing with an existing PDF, you can embed the fonts using Adobe Acrobat Pro DC application.
Note: This process should work OK if you have the same fonts on your computer system that the author had when the PDF was made. However, if the author used a special font or a special character that is not on your system, then it won't work for that portion of the PDF.

For additional information  about embedding the fonts using Acrobat Pro DC application please check out the correct answer marked in the similar discussion: https://community.adobe.com/t5/acrobat/text-changes-to-special-symbols-with-saving-pdf-in-acrobat/m-p/10634321

Hope this infomation will help

Regards

Amal