SSRS: Report converting to PDF insert a blank page

In BIDS, do the following:

1. Click on Report > Report Properties > Layout tab
2. Make a note of the values for Page width, Left margin, Right margin
3. Close and go back to the design surface
4. In the Properties window, select Body
5. Click the + symbol to expand the Size node
6. Make a note of the value for Width

To render in PDF correctly Body Width + Left margin + Right margin must be less than or equal to Page width. When you see blank pages being rendered it is almost always because the body width plus margins is greater than the page width.

Remember: (Body Width + Left margin + Right margin) <= (Page width)

In report properties, set the "ConsumeContainerWhiteSpace" property to True,by default its False. I also had this blank page issue but it was solved by setting this property to True.

This is a bug in SSRS report

You might try this...
Between the tablix's made a rectrangle and place a page breah inside it.
This should force a regular page break at that point.

I found a solution to this and fixed it by using List -component instead of Tablix in the main report. Grouped the List with DataSet property and added one tablix for invoice header -subreport and one tablix below for invoice detail -subreport, both in the same List element (row). For the both tablix properties I set: "Add page break after" and "Keep together on one page if possible". I just have to make sure that the Width of the main report content AND the subreport content does not overflow the page size (A4) and that solved my problem.