a quick Q: how to replace the value quickly

[lina <lina.lastname@gmail.com>]

Hi,

suppose there is a variable in some bash like i, so in some process I used $i so lots,

but I wanna test one long command on terminal,

which as like 
run -a $i.pdf -b $i.pdf -c $i.pdf -d $i.pdf,

how can I change $i very quickly except one by one to
run -a 1.pdf -b 1.pdf -c 1.pdf -d 1.pdf,

Thanks ahead for any suggestions, 


-- 
Best Regards,

lina