I am trying to prepare my thesis for publication and one the requirements is to generate a PDF/A-1B compatible file out of it.
I am using verapdf software to validate my final PDF file and got these three type of error:
- An XObject dictionary shall not contain the SMask key
- For all Type 1 font subsets referenced within a conforming file, the font descriptor dictionary shall include a CharSet string listing the character names defined in the font subset, as described in PDF Reference Table 5.18
- A Group object with an S key with a value of Transparency shall not be included in a form XObject. A Group object with an S key with a value of Transparency shall not be included in a page dictionary
I tried to find out what is their meaning but it is not so easy for me to find a good reference. I think the main source of the problem is the set of my PNG format images.
Any useful advice will be appreciated.