I have created a form in Adobe FormsCentral on a PC but when I download it as a PDF and this PDF is opened on an Apple Mac some of the fields / boxes lose their outlines. This is causing me a problem as I have to use printed forms to collect my data (handwritten by respondents) but the respondents won't be able to see some of the boxes!
It sounds like the users on the Mac are not using Adobe Reader or Adobe Acrobat, FormsCentral PDF forms have features not supported in other PDF viewers and require Adobe Reader or Adobe Acrobat to work, other viewers will break the PDF. There can be a lot of issues outside of the box outlines - see this FAQ for more info: http://forums.adobe.com/docs/DOC-2653
Mac users should download the Free Adobe Reader to fill out the PDF. get.adobe.com/reader/