How to share a document from my MAC to a PC

That would depend on what the document is (Apple Pages or Microsoft Word) for example.

Best way between 2 different platforms is to use a common format such as PDF.

Or create a shared DropBox or Google Drive or iCloud account.

If your source document is Pages, you can EXPORT the document as PDF if you don't want that person to edit or change the document.

The person receiving the document must have Adobe Reader installed.

The other option is to EXPORT it to Word - there are 2 choices: .DOC and DOCX

The person on the PC side must have Word installed and activated in order to view and edit the document.

Also what operating systems are both of you using ?