Thank you for reaching out and sorry for the delay in response.
As I understand you are trying to edit the text in the PDF. If yes, you will need the Adobe Acrobat Pro DC desktop application to edit the PDF. Please refer to the information provided in the following help document to edit PDF: https://helpx.adobe.com/acrobat/using/edit-text-pdfs.html
It seems that you are using Adobe Acrobat Reader DC to open and view PDFs.
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