text annotation looks blurred.

Hi 승희이,

We are sorry for the delay in response to your query.

Could you please share the exact version of Adobe Reader you are working on? Open Reader>Help>Check for update.

Also, it would be more helpful if you will share some screenshot of the blur document?

https://forums.adobe.com/docs/DOC-7043#jive_content_id_How_do_I_attach_a_screenshot

You may also check the commenting preferences  Use annotation and drawing markup tools to add comments in PDFs, Adobe Acrobat and Acrobat Reader https://helpx.adobe.com/acrobat/11/using/commenting-pdfs.html

Adobe Acrobat official update (19.008.20074) is now available. This update will be automatically pushed to all existing installations of Acrobat. If you want, you may also manually trigger the update early by opening the application and going to Help > Check for Updates.

Regards,

Akanchha