Every tablix in SSRS has a property that decides if header rows should be repeated on each page of report. You can chagne this property in Tablix properties:
However, that property is not displayed correctly when exporting to external format, eg. PDF.
If you want to repeat rows heading in tablix in exported file, you have to do as follows:
1. Select tablix
2. In tablix pane, click od down-arrow and check Advanced mode:
3. In Advanced mode, choose every (Static) element in Row Groups pane, that you want to repeat on new page. While you selected this element, you have to change “Static row” properties KeepWithGroup = After and RepeatOnNewPage =True:
Every (Static) is a single header row displayed in tablix, eg. simple table with one header row have one (Static).
That solution works when you export SSRS reports to PDF and DOCX using SSRS native export feature.
Hope this helps 😉