When uploading PDF files, best practice would be to make sure your product's Item Name and the filename you're uploading are only using Latin ASCII characters using plain, unaccented uppercase or lowercase letters (A-Z, a-z), numerals (0-9), dashes- and _underscores, and one dot (.) only before the filename extension at the end.
It would be best to avoid using non-Latin alphabet characters (e.g., Cyrillic, Korean, etc.), accented letters (e.g. á ç è ø ü, etc.), other punctuation or symbols, or filenames that include spaces or any additional dots (besides the final extension), as those can sometimes cause a problem.
You can temporarily rename the product's Item Name, if there are any special characters or symbols, before uploading your file, then change the Item Name back once the upload is complete. However, I wouldn't include the tilde in the actual PDF file name as that could still cause problems. Additionally, any spaces left in the PDF file name will be replaced by underscores in the downloaded file name.
