Forced restart of mobile phone, system upgrade or software upgrade.
If this is still the case, I suggest you install anti-virus software to kill virus on your mobile phone.
If it is not solved, it is recommended that you restore your mobile phone to its factory settings.
You can download the PDF editor and install it on your computer. You just need to search for "quick PDF editor" on the Internet, find relevant websites, download, install and run.
Open the software, click "Open" in "File" and a dialog box will pop up. Go to the folder where you saved the e-book and open the e-book you want to edit. Click on the page to be edited in the number of pages on the left to see what is displayed in the PDF file.
We just need to select the text box where the garbled words are and delete it. If you want to add text to it, you can delete it directly and enter the text in the text box. When you are finished, click Save or output directly as a PDF document.
If the above methods can't solve the problem of garbled code, it's mostly the motherboard problem. It is recommended that you send your mobile phone to after-sales service outlets for testing and maintenance.