if i scan some documents then i convert into PDF's files and i want to remove some text from these documents.How can i do it?

You can use Edit PDF tool for this. After converting scanned document to PDF, go to Edit PDF tool in Acrobat.

It will run text recognition tool. Now you can remove extra text you do not want.

If you do not have Adobe Acrobat installed, you can use trial version of latest Adobe Acrobat DC Download Adobe Acrobat free trial | Acrobat Pro DC

Hope it will resolve your issue. Please feel free to ask anything you want.

Thanks.