Looking at the description above, I believe you have received a form to fill it and send it back to the recipient. There are a few things we need to check.
How exactly you are filling the form and how did you receive it? Was it opened through Adobe Acrobat/Reader DC desktop application or you opened it directly from attachment itself? Please share your exact workflow step-by-step
If you are working on Mac computer, was this pdf form filled using Mac preview? Its a know issue with preview, a form filed using Preview doesn't shows the data, unless you don't click on it.
You need to download the form first>Open it using Acrobat/Reader DC desktop application>Fill it and send it back.
Hello good afternoon. It is not a form. It is a text file transformed into a pdf. I highlight something in the pdf and send it to someone or attached to a file. When this is done, the highlight disappears. Thanks!!!