Storage plans and pricing are available at http://www.zotero.org/support/storage.
You can maximize your storage space by disabling automatic attachments (see the recommended set up instructions for further information) and/or by linking to files stored on your hard drive instead of storing files on the Zotero.org server. This is the difference between "linked files" and "stored files." Linked files create a path to a file stored on your computer. The caveat is that they do no sync (not accessible from multiple computers) and are not shareable in group libraries. Stored files are copied onto your Zotero.org server space, sync, are accessible from any computer, and can be shared in group libraries (and take up storage space).
No. However, you can use Zotero with a PDF reader that allows markups. You can also sync Zotero with Mendeley, another citation management program that does allow for PDF note taking. Keep in mind that Zotero does offer the Notes attachment, where you can jot down whatever you need and copy and paste relevant quotes.
Yes, but only if you are willing to work with some basic coding modification of the Citation Style Language. However, as the documentation page on citation styles notes, you can request a style as an alternative route. To create the style yourself, follow the directions on the documentation pages for editing CSL styles. You do not have to be formally trained in computer coding to make small modifications to an existing style as there are some helpful tools and documentation. However, you do need patience, attention to detail, and a willingness to experiment.
Yes. See instructions for creating multiple Zotero profiles
Troubleshooting tips can be found in the Zotero documentation.
It may be necessary to manually install the Word plug-in.
Zotero is an open source tool. It was developed by the Center for New Media at George Mason University with funding from the United States Insitute for Museum and Library Sciences and the Alfred P. Sloan Foundation. It is freely available community tool, so anyone can contribute to its development. This also means that there is no 1-800 number for support.
Zotero recommends that you follow these steps to troubleshoot: