PDF won't save, Adobe Acrobat

I am trying to save a secured and confidential document (on my Macbook Air), but it won't let me. I've filled it in and when I click on save, it says "the file may be read-only, or another user may have it open. please save the document with a different name or in a different folder". So I try the "save as" option and try to change the name of the document and where I save it, it tells me "the document could not be saved. bad parameter". I then try to reduce the file size and it tells me that "this pdf contains an adobe XML form. Such files cannot be optimized". 

If I try to start filling up the document all over again, it starts a whole other problem with my javascript. 

Can I  please get some help on saving this document. Thank you.