Unless you know the password and remove the security policy, you can't edit it.
I was able to edit it by Save As and choose another name then I had access to the edit tools. Very strange!
Why was a able to edit by saving as a different name and not being able to edit with the original?
Did you do save as or save a copy? If the latter then the file had the Extended Reader Rights applied to it, which prevented you from editing it. Saving a copy of it removes those rights.
That would indicate the PDF was a form and that PDF had some special form rights applied to the PDF. Because one PDF behaves this way does not mean all PDFs will behave this way.
If the creator of the PDF were to assign a password to allow editing of a form, your saving as approach will not work because the applied password overrides the restriction appliec by enabling form rights.