We are sorry for the trouble. As described you want the PDF forms to be shared with customers via Adobe Acrobat Reader DC that doesn't allow changes to the form .
Adobe Acrobat Reader DC is a freeware application, with limited functionality. It is used for viewing, printing, signing, sharing, and annotating PDFs. We can not set the security of the document with Acrobat Reader DC. For more information please look at the help page https://helpx.adobe.com/in/reader/faq.html
Using Acrobat you can flatten the fields, which would convert their values to static contents. Note that this is not reversible, so make sure to keep a copy of the unflattened file, in case you want to make changes to it later on.
The easiest way to flatten a file is by running this script on it: