For A4 pdf-s you need at least a 9.7-inch screen. Technically, this is about A5 size, but without margins you can display an A4 page with minimal reduction in size. (With an 8-inch screen you will usually need to go into landscape view and move around the page, which slows things down and can be unpleasant.)
There are only a few 10-inch e-ink readers on the market, and - as far as I know - only one of them has a frontlight: the Hanvon E930. This is not sold in Europe, you need to buy it from China. You can read my first impressions here:
https://www.mobileread.com/forums/sho...d.php?t=254273
It has no browser and no English dictionary, but pdf handling is fine - I tested it with a 200MB, 860-page scanned pdf.
I have also used the Onyx Boox M92. Pdf handling is fine (tested as above), touch screen is stylus-only, dictionary installation is possible, and it has a browser.
The Irex DR1000S can be found sometimes on Ebay around 200 USD as a used reader. It is an older device, but if you're on a budget, it's not a bad choice: stylus-only touch screen, no browser, but fine pdf handling (tested with the large document mentioned above).
All of those three devices also support writing on the screen with a stylus. The M92 and the Irex also support multi-tasking, so you can quickly switch between documents or between a document and your notes.
Probably the most versatile large reader is the Onyx Boox M96 (with stylus-only electromagnetic screen) or its brother, the M96C (with finger-only capacitive screen). They run open Android, so you can install various applications - but they lack a frontlight.
I hope this helps in your selection!