An "invalid digital signature" error in a PDF typically means that the digital signature applied to the PDF document is not valid or has been tampered with in some way. Digital signatures are used to verify the authenticity and integrity of a document. When a PDF has a valid digital signature, it means that the document has not been altered since it was signed and that the signature was generated by a trusted source.
How to solve Invalid Signature Issue (Red Cross):
- Open PDF File in Foxit PDF Reader
- Right Click on Red Crossed Invalid Signature and select View Signed Version Option
- Usually PDF File gets Green Sign here but if Still Red Cross then it will ask for update Certificate. Just click OK as shown below:
- After it Left Click on Signature and Signature Validation Status Popup will appear. Click on Signature Properties...
- In Signature Properties window click on Show Certificate:
- In New Window Click on Trust Tab and click on Add to Trusted Certificate:
- Click OK. close all popups and Again Left Click on Red Cross icon. and bingooooo