If you have multiple artboards to export in one pdf with artboard name on each artboard.
Here is the thing you can do on sketchApp:
1.) Firstly give names to all artboards above them manually with Text field. Check out the attachment for more clarification.
2.) Multiple ways to use Slice function in SketchApp, you can simply press "S" and slice will activate and another way is clicking on insert button on top left corner you can select Slice from the list.
3.) Using slice you can slice all the artboards at one like you are taking a screenshot of all the artboards at once.
4.) Slice has an export function so you can select the format(jpg,pdf,png,etc.) how you want to export the slice selected by you.
5.) You can also change background color before exporting the slice, also you can rename that slice like we do for all artboards.
Hope I understood your question correctly and this answer helps you. if you still have confusion you can reply to comments.
Thanks
SketchApp screen for slice function
multiple artboard exported image