Email Attachment: Is it the file indexed in Google search results?

My company is looking for a way to have the form send the an email with certain sensible information (only available to those who complete the form). We are concerned that google may be able to find said document and make it available for everyone. Is it safe to make such a document an attachement for the autoresponse email? please respond also as to where would this document be hosted? 

The file will not be indexed in Google results, this is because the file is attached as if you would be sending if via email. 

For example, I used a Gmail address and this is how the attachment looks like: 

If you check the attached file's link you will notice it's like this one: https://mail-attachment.googleusercontent.com/attachment/u/1/?ui=2&ik=b0318fd019&view=att&th=15dc41eb4a3a953d&attid=0.1&disp=inline&safe=1&zw&saddbat=ANGjdJ9Yrv-Ymg51VXvUo_yafu3vH2zJ6EJmb_zXdktupv-DutmCz32xFzYUoIZ1Rvs2Mii0L7jvsfyDUY0C4ZKH9tNAnuCR4VLPUjpuNi31SKx910GmETZRUhdkVdV2srxkvwiNuHVLd-9lISx1u6RxOkdimNjaS2QLUiR5KR5xn94N54aWs_PMs9_gsB9RNvcf9cxoCtQoP750z7YAYR1zjyw8OhXk4hiAmjrMMy-z2i3vT4oOjwXYVEG8fZcLwP6YetngqgJByURZxTFNqiAwR6fPG6ALJgmsXfPqKD3KraCcyj4dQnFIyiGvcvoNVwSfefE2ajR5Ya5KOBCiyiMgcd8vGh2ufeZsfrd24IcDMrwtvMI7qEP3HtpkngVMCYu6U6qaHXyM9HKZwjn6nlGVPzphxJoitp9r7ENi25IQGvmXuLzvLNLUq5DVRkWHqu65_InU7ZTmf-L-CLt3cA7JVzlWrlFpFRafxAdUPGXSpAtc0ODrD1UUZIVMw0G6xdIDPlMSOucXJjxZa8eP-0Gk0pCvn1aFYwPKWJO3K6LyCgsoevpx6PJCjVsPNm5Mz2KEuxwLJrS3CCcJ36jVH8uUXIz_ypUJSpSw6GwdO2NwVNAfPlsbqMAQ5EOifZ0 

That link is already protected by Google since if you try to load it you will be asked to log-in into the account where the file was sent in order to access it. 

The same will happen with other email providers, for example, Outlook will provide the attached file like this: https://outlook.live.com/owa/#viewmodel=IAttachmentViewModelPopoutFactory&wid=60&ispopout=1 

I hope this helps.