Acrofields created with libre office are not code fillable unless I edit the pdf once - itext

Question

I am creating a form control in Libre office and am exporting the document to pdf.
Trying to set the text of the control (a textbox) using itextsharp (in other words c# program) only empties the box.
However, if I open the pdf using acrobat reader and edits the text in the box, saving the document results in a pdf where it is possible to write to that textbox.
Why do I have to do that?
Error reproduction
Cliking the toolbar icon in libre office.
Dragging out a square in the document.
Double clicking that box, giving it the name currenttime.
Exporting to pdf:
c# code
if (openFileDialog1.ShowDialog() == DialogResult.OK)
{
if (saveFileDialog1.ShowDialog() == DialogResult.OK)
{
using (var fs = new FileStream(saveFileDialog1.FileName, FileMode.Create))
{
var reader = new PdfReader(openFileDialog1.FileName);
{
using (var pdfStamper = new PdfStamper(reader, fs))
{
var acroFields = pdfStamper.AcroFields;
acroFields.SetField("currentdate", DateTime.Now.ToString());
pdfStamper.FormFlattening = true;
pdfStamper.FreeTextFlattening = true;
pdfStamper.Writer.CloseStream = false;
}
}
reader.Close();
fs.Close();
}
}
}
edit
Here comes textual dumps of the pdf. I have changed some binary data places with "some binary data". The textbox has been given the default value "123".
pdf after it has been created with libre office is of version 1.4
%PDF-1.4
some binary data
2 0 obj
<</Length 3 0 R/Filter/FlateDecode>>
stream
some binary data
endstream
endobj
3 0 obj
78
endobj
7 0 obj
<</Type/FontDescriptor/FontName/LiberationSans
/Flags 4
/FontBBox[-543 -303 1301 980]/ItalicAngle 0
/Ascent 905
/Descent -211
/CapHeight 979
/StemV 80
>>
endobj
8 0 obj
<</Type/Font/Subtype/TrueType/BaseFont/LiberationSans
/Encoding/WinAnsiEncoding
/FirstChar 32 /LastChar 255
/Widths[277 277 354 556 556 889 666 190 333 333 389 583 277 333 277 277
556 556 556 556 556 556 556 556 556 556 277 277 583 583 583 556
1015 666 666 722 722 666 610 777 722 277 500 666 556 833 722 777
666 777 722 666 610 722 666 943 666 666 610 277 277 277 469 556
333 556 556 500 556 556 277 556 556 222 222 500 222 833 556 556
556 556 333 500 277 556 500 722 500 500 500 333 259 333 583 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
277 333 556 556 556 556 259 556 333 736 370 556 583 333 736 552
399 548 333 333 333 576 537 333 333 333 365 556 833 833 833 610
666 666 666 666 666 666 1000 722 666 666 666 666 277 277 277 277
722 722 777 777 777 777 777 583 777 722 722 722 722 666 666 610
556 556 556 556 556 556 889 500 556 556 556 556 277 277 277 277
556 556 556 556 556 556 556 548 610 556 556 556 556 500 556 500
]
/FontDescriptor 7 0 R>>
endobj
5 0 obj
<</F1 8 0 R
>>
endobj
9 0 obj
<</Font 5 0 R
/ProcSet[/PDF/Text]
>>
endobj
1 0 obj
<</Type/Page/Parent 6 0 R/Resources 9 0 R/MediaBox[0 0 595 842]/Annots[
4 0 R ]
/Group<</S/Transparency/CS/DeviceRGB/I true>>/Contents 2 0 R>>
endobj
6 0 obj
<</Type/Pages
/Resources 9 0 R
/MediaBox[ 0 0 595 842 ]
/Kids[ 1 0 R ]
/Count 1>>
endobj
10 0 obj
<</Type/XObject
/Subtype/Form
/BBox[0 0 82.7 23.1]
/Resources 9 0 R
/Length 18
/Filter/FlateDecode
>>
stream
some binary data
endstream
endobj
4 0 obj
<</Type/Annot/Subtype/Widget/F 4
/Rect[59.6 759.3 142.5 782.2]
/FT/Tx
/P 1 0 R
/T(currenttime)
/Ff 4096
/V <FEFF003100320033>
/DV <FEFF003100320033>
/DR<</Font 5 0 R>>
/DA(0 0 0 rg /F1 12 Tf)
/AP<<
/N 10 0 R
>>
>>
endobj
11 0 obj
<</Type/Catalog/Pages 6 0 R
/OpenAction[1 0 R /XYZ null null 0]
/Lang(sv-SE)
/AcroForm<</Fields[
4 0 R
]/DR 9 0 R/NeedAppearances true>>
>>
endobj
12 0 obj
<</Creator<FEFF005700720069007400650072>
/Producer<FEFF004C0069006200720065004F0066006600690063006500200035002E0033>
/CreationDate(D:20170606104859+02'00')>>
endobj
xref
0 13
0000000000 65535 f
0000001431 00000 n
0000000019 00000 n
0000000168 00000 n
0000001843 00000 n
0000001347 00000 n
0000001590 00000 n
0000000187 00000 n
0000000357 00000 n
0000001378 00000 n
0000001688 00000 n
0000002073 00000 n
0000002231 00000 n
trailer
<</Size 13/Root 11 0 R
/Info 12 0 R
/ID [ <5F5DD24A5E7FF740A8BB6B15F88EF602>
<5F5DD24A5E7FF740A8BB6B15F88EF602> ]
/DocChecksum /BFFAD3050AA9FF87945C97B9608B3C6C
>>
startxref
2406
%%EOF
after it has been edited in acrobat reader (I changed the default value of the textbox from "123" to "12"), it will be saved in version 1.6 and an interesting x:xmpmeta information is inserted. Also a lot of empty lines are inserted in the document. At this point, it is programmatically editable.
%PDF-1.6
%âãÏÓ
7 0 obj
<</Linearized 1/L 6449/O 9/E 2599/N 1/T 6160/H [ 451 149]>>
endobj
13 0 obj
<</DecodeParms<</Columns 4/Predictor 12>>/Filter/FlateDecode/ID[<5F5DD24A5E7FF740A8BB6B15F88EF602><FAE65369E246E7409111A7D5BDED1E6F>]/Index[7 17]/Info 6 0 R/Length 52/Prev 6161/Root 8 0 R/Size 24/Type/XRef/W[1 2 1]>>stream
some binary data
endstream
endobj
startxref
0
%%EOF
23 0 obj
<</Filter/FlateDecode/I 92/Length 65/S 38/V 69>>stream
some binary data
endstream
endobj
8 0 obj
<</AcroForm<</DA(/Helv 0 Tf 0 g )/DR 22 0 R/Fields[14 0 R]>>/Lang(sv-SE)/Metadata 1 0 R/OpenAction[9 0 R/XYZ null null 0]/Pages 5 0 R/Type/Catalog>>
endobj
9 0 obj
<</Annots[14 0 R]/Contents 12 0 R/CropBox[0 0 595 842]/Group<</CS/DeviceRGB/I true/S/Transparency>>/MediaBox[0 0 595 842]/Parent 5 0 R/Resources 22 0 R/Rotate 0/Type/Page>>
endobj
10 0 obj
<</BBox[0.0 0.0 82.9 22.9]/Filter/FlateDecode/Length 68/Resources 15 0 R>>stream
some binary data
endstream
endobj
11 0 obj
<</Filter/FlateDecode/First 66/Length 1226/N 9/Type/ObjStm>>stream
some binary data
endstream
endobj
12 0 obj
<</Filter/FlateDecode/Length 78>>stream
some binary data
endstream
endobj
1 0 obj
<</Length 3146/Subtype/XML/Type/Metadata>>stream
<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>
<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 5.4-c005 78.147326, 2012/08/23-13:03:03 ">
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<rdf:Description rdf:about=""
xmlns:xmp="http://ns.adobe.com/xap/1.0/"
xmlns:pdf="http://ns.adobe.com/pdf/1.3/"
xmlns:xmpMM="http://ns.adobe.com/xap/1.0/mm/"
xmlns:dc="http://purl.org/dc/elements/1.1/">
<xmp:CreateDate>2017-06-06T10:48:59+02:00</xmp:CreateDate>
<xmp:CreatorTool>Writer</xmp:CreatorTool>
<xmp:ModifyDate>2017-06-06T11:20:41+02:00</xmp:ModifyDate>
<xmp:MetadataDate>2017-06-06T11:20:41+02:00</xmp:MetadataDate>
<pdf:Producer>LibreOffice 5.3</pdf:Producer>
<xmpMM:DocumentID>uuid:fcdf7344-18ca-44b6-934c-8d5ab8fc8ea3</xmpMM:DocumentID>
<xmpMM:InstanceID>uuid:895fdc09-0aaa-4421-86b2-418c75f88d22</xmpMM:InstanceID>
<dc:format>application/pdf</dc:format>
</rdf:Description>
</rdf:RDF>
</x:xmpmeta>
<?xpacket end="w"?>
endstream
endobj
2 0 obj
<</Filter/FlateDecode/First 4/Length 48/N 1/Type/ObjStm>>stream
some binary data
endstream
endobj
3 0 obj
<</Filter/FlateDecode/First 4/Length 106/N 1/Type/ObjStm>>stream
some binary data
endstream
endobj
4 0 obj
<</DecodeParms<</Columns 3/Predictor 12>>/Filter/FlateDecode/ID[<5F5DD24A5E7FF740A8BB6B15F88EF602><FAE65369E246E7409111A7D5BDED1E6F>]/Info 6 0 R/Length 37/Root 8 0 R/Size 7/Type/XRef/W[1 2 0]>>stream
some binary data
endstream
endobj
startxref
116
%%EOF
edit2
I was putting the files on my dropbox.
https://www.dropbox.com/sh/5btzl9qqzua18q1/AACIjCrvNZ5cunuLj9sze-l3a?dl=0

Answer 1

As already surmised in a comment, the problem is caused by Libre Office creating the PDF with NeedAppearances set to true in the AcroForm dictionary. Furthermore the wrong field name is used.
Field name
In your code you set the field "currentdate" while in your sample PDFs the field is called "currenttime". Obviously you have to use the correct field name.
NeedAppearances flag
This flag tells a PDF viewer that it shall construct appearance streams and appearance dictionaries for all widget annotations in the document. iText, therefore, when filling in the form field
acroFields.SetField("currentdate", DateTime.Now.ToString());
does not create an appearance for that field - any viewer is required to construct new appearances anyways.
Unfortunately form flattening
pdfStamper.FormFlattening = true;
is implemented by using the existing appearances and only them. As no appearance has been created when setting the field, its flattened form turns out to be empty.
(Strictly speaking this implementation of form flattening is wrong: In this case iText is the PDF processor that wants to make use of the appearances; thus, it should create all appearances here, even ignoring existing ones.)
You can fix this by telling iText to create appearances during form fill-ins in spite of the NeedAppearances flag:
using (var pdfStamper = new PdfStamper(reader, fs))
{
var acroFields = pdfStamper.AcroFields;
acroFields.GenerateAppearances = true;// <<<<<<<<<<<<<<<<<<
acroFields.SetField("currenttime", DateTime.Now.ToString());
pdfStamper.FormFlattening = true;
pdfStamper.FreeTextFlattening = true;
pdfStamper.Writer.CloseStream = false;
}
After adding the marked line above, the output of the code includes the changed newly set value.
Additionally Libre Office does not embed the LiberationSans font. As I have not installed it on my system, I only see dots. I would propose you make LibreOffice embed such fonts or else use standard 14 fonts. Otherwise your PDFs won't display as desired on a number of computers.