docdrop url mismatch with H api

### Steps to reproduce
1. to access the docdrop annotations through H web client the url is https://docdrop.org/pdf/HowPeopleLearn_Ch2-34ovo.pdf/
2. To access the docdrop annotations through the H api the url is https://docdrop.org/static/drop-pdf/HowPeopleLearn_Ch2-34ovo.pdf/
3.

### Expected behaviour
Tell us what should happen.
The two urls should be the same.

### Actual behaviour
Tell us what happens instead.
There is a mismatch between the url used for the h web client goes and the url for the h api

### Browser/system information
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you encountered this issue.

### Additional details
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one.