"CIDFont+F1" (and variations like F1Normal) is not typically a font you can download like a standard typeface. Instead, it is a generated by software when an original font fails to embed properly in a PDF document. What is CIDFont+F1?
Open your problematic PDF in a text editor (like Notepad++) or use Adobe Acrobat Pro’s "Preflight" tool to check the font mapping. Look for a line like: /F1Normal /Helvetica /CIDFont cidfont f1normal font free download new