I want to import a PDF with multiple pages into Photoshop. The PDF contains tables which have a shading behind the row names and column names in the first column and row. Is there some way to use Photoshop to modify this filling? Maybe to somehow detect this rectangular a object and then adjust the colour of something?
Unless the PDF was saved from Photoshop, with "Retain Photoshop Editing capabilities" checked, there is no way to split a PDF into elements.
Photoshop only rasterizes whole pages when you open a PDF generated from anything other than Photoshop.
You may have better luck opening the PDF in Illustrator, then if needed export the Illustrator file to a .psd.