I 'm trying to create a visible signature in a PDF file.
Taking a simple PDF "hello world" file:
%PDF-1.7
1 0 obj % entry point
<<
/Type /Catalog
/Pages 2 0 R
>>
endobj
2 0 obj
<<
/Type /Pages
/MediaBox [ 0 0 200 200 ]
/Count 1
/Kids [ 3 0 R ]
>>
endobj
3 0 obj
<<
/Type /Page
/Parent 2 0 R
/Resources <<
/Font <<
/F1 4 0 R
>>
>>
/Contents 5 0 R
>>
endobj
4 0 obj
<<
/Type /Font
/Subtype /Type1
/BaseFont /Times-Roman
>>
endobj
5 0 obj % page content
<<
/Length 44
>>
stream
BT
10 05 TD
/F1 12 Tf
(Hello, world!) Tj
ET
endstream
endobj
xref
0 6
0000000000 65535 f
0000000010 00000 n
0000000079 00000 n
0000000173 00000 n
0000000301 00000 n
0000000380 00000 n
trailer
<<
/Size 6
/Root 1 0 R
>>
startxref
492
%%EOF
And signing it with a text to appear "Yolo" at some position at the first page produces this:
%PDF-1.7
1 0 obj % entry point
<<
/Type /Catalog
/Pages 2 0 R
>>
endobj
2 0 obj
<<
/Type /Pages
/MediaBox [ 0 0 200 200 ]
/Count 1
/Kids [ 3 0 R ]
>>
endobj
3 0 obj
<<
/Type /Page
/Parent 2 0 R
/Resources <<
/Font <<
/F1 4 0 R
>>
>>
/Contents 5 0 R
>>
endobj
4 0 obj
<<
/Type /Font
/Subtype /Type1
/BaseFont /Times-Roman
>>
endobj
5 0 obj % page content
<<
/Length 44
>>
stream
BT
10 05 TD
/F1 12 Tf
(Hello, world!) Tj
ET
endstream
endobj
xref
0 6
0000000000 65535 f
0000000010 00000 n
0000000079 00000 n
0000000173 00000 n
0000000301 00000 n
0000000380 00000 n
trailer
<<
/Size 6
/Root 1 0 R
>>
startxref
492
%%EOF
8 0 obj
<</F 132/Type/Annot/Subtype/Widget/Rect[0 0 0 0]/FT/Sig/DR<<>>/T(Signature1)/V 6 0 R/P 3 0 R/AP<</N 7 0 R>>>>
endobj
6 0 obj
<</Contents <...>/Type/Sig/SubFilter/ETSI.CAdES.detached/M(D:20190626125540+00'00')/ByteRange [0 824 60826 1401]/Filter/Adobe.PPKLite>>
endobj
9 0 obj
<</BaseFont/Helvetica/Type/Font/Subtype/Type1/Encoding/WinAnsiEncoding/Name/Helv>>
endobj
10 0 obj
<</BaseFont/ZapfDingbats/Type/Font/Subtype/Type1/Name/ZaDb>>
endobj
12 0 obj
<</Length 35>>stream
BT
1 15 TD
/Helv 6 Tf
(Yolo) Tj
ET
endstream
endobj
7 0 obj
<</Type/XObject/Resources<</ProcSet [/PDF /Text /ImageB /ImageC /ImageI]>>/Subtype/Form/BBox[0 0 0 0]/Matrix [1 0 0 1 0 0]/Length 8/FormType 1/Filter/FlateDecode>>stream
xœ
endstream
endobj
3 0 obj
<</Type/Page/Parent 2 0 R/Resources<</Font<</F1 4 0 R>>>>/Contents [12 0 R 5 0 R]/Annots[8 0 R]>>
endobj
2 0 obj
<</Type/Pages/MediaBox[0 0 200 200]/Count 1/Kids[3 0 R]>>
endobj
1 0 obj
<</AcroForm<</Fields[8 0 R]/DR<</Font<</Helv 9 0 R/ZaDb 10 0 R>>>>/DA(/Helv 0 Tf 0 g )/SigFlags 3>>/Type/Catalog/Pages 2 0 R>>
endobj
11 0 obj
<</Producer(AdES Tools https://www.turboirc.com)/ModDate(D:20190626125540+00'00')>>
endobj
xref
0 4
0000000000 65535 f
0000061604 00000 n
0000061529 00000 n
0000061414 00000 n
6 7
0000000804 00000 n
0000000000 65535 f
0000000679 00000 n
0000060952 00000 n
0000061050 00000 n
0000061746 00000 n
0000061127 00000 n
trailer
<</Root 1 0 R/Prev 492/Info 11 0 R/Size 17/ID[<4BB225C2F629BB21464F66FBF2FED264><8E3C9AD8354C66931EAAC282088455EA>]>>
startxref
61846
%%EOF
So there is an object in the PDF that shows some text in the first page:
12 0 obj
<</Length 35>>stream
BT
1 15 TD
/Helv 6 Tf
(Yolo) Tj
ET
endstream
endobj
My problem is now that this object is treated like a common text object in adobe reader. I want it, when clicked, to go to the digital signature, like how Adobe Acrobat signs the documents.
What do I miss? Is there a parameter in the digital signature (The 6 or 8 number object) or in any of the other objects my app puts in the new PDF that links the text object with the signature?
Thanks a lot.
Your object 8
8 0 obj
<</F 132/Type/Annot/Subtype/Widget/Rect[0 0 0 0]/FT/Sig/DR<<>>/T(Signature1)/V 6 0 R/P 3 0 R/AP<</N 7 0 R>>>>
endobj
is an AcroForm form field for signatures (as the FT entry with value Sig tells us). At the same time, though, this object also is a form field widget annotation (as can be seen in the Type and Subtype entries). Form field widget annotations are the visual representations of form fields, and if a form field has only one representation, the widget can be merged with the form field as in your object.
In your case the annotation has a 0x0 size (/Rect[0 0 0 0]), i.e. invisible. To have a visible representation, you need an annotation rectangle that does not vanish.
The content that is displayed is defined in the normal appearance /AP<</N 7 0 R>> which points to object 7.
7 0 obj
<</Type/XObject/Resources<</ProcSet [/PDF /Text /ImageB /ImageC /ImageI]>>/Subtype/Form/BBox[0 0 0 0]/Matrix [1 0 0 1 0 0]/Length 8/FormType 1/Filter/FlateDecode>>stream
xœ
endstream
endobj
At first glance this looks pretty empty, even after decompression.
Thus, what you have to do is
Furthermore you should fix obvious errors in your PDF, e.g.
For details please study the PDF specification ISO 32000. Part 1 is published for download by Adobe at https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/PDF32000_2008.pdf
In particular sections