Adding a cross-reference field within a document is easy enough, I just hit reference>cross-reference and can point to any number in a list, which will update automatically if I make changes to the list.

But how do I cross-reference a number field in an outside document?

For example, Document A is a list like this:

1. [Facts about John]
2. [Facts about Sally]


3. [Facts about Jeremy]

Document B has texts such as: "see Document A, paragraph (1) for facts about John..."

If I change my list to the following:

1. [Facts about Steve]
2. [Facts about John]
2. [Facts about Sally]
3. [Facts about Jeremy]

I want Document B to automatically update the cross-reference number to say "see Document A, paragraph (2) for facts about John..."

This is easily achieved when the list is within Document B, but how can I achieve this when dealing with 2 separate documents?

What you need for that is an INCLUDETEXT field that references the bookmark in the other document. See under Insert>Quick Parts>Field.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

How do I bookmark a paragraph number?

If, in the source document, you insert a cross-reference to the paragraph in question, Word will automatically bookmark it selecting the cross-reference and pressing Dhift-F9 will reveal the bookmark name Word has assigned. The INCLUDETEXT field can then reference that bookmark.

However, if all you want to do is to reference the paragraph number in the source, a slightly different approach is required:
• In the source document, insert a cross-reference to the paragraph, using the 'paragraph number' option.
• Select the inserted cross-reference and press Shift-F9 the enclose it in a pair of field braces (e.g. { 4.2 })
• Edit the field, so as to turn it into a SET field, thus: {SET BkMk "4.2"}, where BkMk is a bookmark name, then press F9 to update the field (which will disappear).
• In the target document an INCLUDETEXT field that references the bookmark used in the SET field.

Note: since you won't be able to see the SET field, making it prone to accidental deletion, it might be best to create it in the document header or footer, where it is less likely to be deleted by accident.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]