In the unlikely event that the header rows are always formatted with the
same unique style, and the rest of the rows are formatted with another
unique style, you can do what you want simply by modifying the table styles
that are being used.
If the document originator accepted Word's defaults, then the style applied
to all of your tables most likely is the Table Grid style. If that's the
case, then you might be able to accomplish at least half of your chore using
styles.
Click in the first table. Choose Format - Styles and Formatting, and
observer the "Formatting of selected text. Is it Table Grid? If so, then
right-click it in the list and choose Modify. At the bottom, choose Format -
Table Properties. In the Row tab, click to check Allow row to break across
pages. Click OK- OK.
Assuming that "Allow to break..." has not been previously removed through
direct formatting. This will take care of the Allow to break... problem.
The "Repeat as header row..." problem is a bit more difficult. That's
because it must be applied to the row(s) you actually want to repeat.
Assuming you want only the top row in each table to be repeated, the
technique I can think of to do it without macros and using the mouse is as
follows (with the insertion point at the top of the document):
1. Put the Repeat tool onto a toolbar (Tools - Customize - Commands tab -
Edit category - drag the Repeat tool to a toolbar).
2. Create a new style, perhaps called Table Header Row, and assign the
"Repeat as header row..." formatting as part of that style's definition.
3. Set the Browse Object to tables (click the middle button at the bottom of
the vertical scroll bar and choose Browse by table; click the Browse Next
Table button.
4. Apply the Table Header Row style to the row where the insertion point is
located.
5. Click the Browse Next Table button.
6. Click the Repeat tool.
Alternate steps 5 & 6 until all of the top rows of all of the tables have
been formatted with the Table Header Row style.