All of the icons of the pdf files are grey, meaning that they can’t be uploaded in GPT-o1.
But pdf files can be uploaded normally in other models such as GPT-4o.
Hi @Anna_Yanami 
Currently, the only type of file you can upload to o1 models are images.
You cannot upload non image files (for now).
I hope OpenAI is improving it, and we can upload other files soon.
Please visit following link: