com.itextpdf.*
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"DefaultAppearance is required but not found"
"A noninvertible matrix has been parsed. The behaviour is unpredictable."
"PdfDocument must be opened in stamping mode."
"Unsupported image type"
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"Cannot obtain image info after filtering."
"Failed to process a transformation matrix which is noninvertible. Some content may be placed not as expected."
"Partial clean up of transparent images with mask encoded with one of the following filters is not supported: JBIG2Decode, DCTDecode, JPXDecode. Image will become non-transparent."
"Redaction of annotation subtype /Watermark is not supported"