An interactive Word document does not convert to an interactive PDF document - you will have to add the interactive elements manually (or let Acrobat do it for you).
In Adobe Acrobat DC (this will not work in the free Reader), select the "Prepare Forms" option in the panel on the right side, or click on "Tools" and then select "Prepare Forms" from the list if icons.
On the next dialog, you will select which document you want to process. At the bottom of that dialog you will see something like this:
If you want Acrobat to try to detect you fields (which is very unreliable), then the "Form field auto detection" should be set to "ON". If it's not, click on the "Change" button and change it in Acrobat's preferences. If you don't have too many checkboxes, I would make sure that this setting is set to "OFF" - it makes your life a bit easier, trust me :)
Once you are in the form editor mode, just add checkboxes to your document. You will probably have to resize the first one. Do that and put it on top of the box in your PDF file. Then bring up the box properties (e.g. right-click and select Properties, or double-click on the box in the editor). Now go to he "Appearance" tab and set both the fill color and the stroke color to "transparent" - you already have a box in your document, there is no need to draw another one.
Once you've set up the first checkbox the way you want it, right-click on the checkbox again and select "Use current properties as new defaults" so that all checkboxes you generate from now on will match the one that you've just created.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com