如何使用C#程序给PDF文件添加编辑域

pdf文档通常是不能编辑的，但有些时候需要在pdf文档中填写日期或签名之类，就需要在pdf有能编辑的文本域，本文介绍怎样用c#来实现这一功能。

环境

工具：vs2015

语言：c#

操作pdf类库：itextsharp 5.5.10

生成的pdf预览的工具：skim、福昕阅读器、acrobat reader

代码实现

获取文档的页数

pdfreader reader = new pdfreader(@"c:\workspace\1.pdf");
int count = reader.numberofpages;

创建文本域

textfield fielddate = new textfield(stamp.writer, new itextsharp.text.rectangle(105, 100, 240, 125), "date");
fielddate.backgroundcolor= basecolor.white;fielddate.borderwidth= 1;
fielddate.bordercolor= basecolor.black;fielddate.borderstyle= 4;
fielddate.fontsize = 11f;

itextsharp.text.rectangle(105, 100, 240, 125) 用来设置文本域的位置，四个参数分别为：llx、lly、urx、ury：

llx 为left ，lly 为bottom,urx 为right，ury 为top
其中：width=right - left heigth = top - bototom
创建文本

chunk cname = new chunk("date:", fontfactory.getfont("futura", 16f,new basecolor(170,64,0)));
phrase pname = new phrase(cname);
pdfcontentbyte over = stamp.getovercontent(count);
columntext.showtextaligned(over, element.align_center, pname, 400, 420, 0);

完整代码

public static void addtextfield()
{
   pdfreader reader = new pdfreader(@"c:\workspace\1.pdf");
      
   filestream out1 = new filestream(@"c:\workspace\2.pdf", filemode.create, fileaccess.write);

   pdfstamper stamp = new pdfstamper(reader, out1);
      //获得pdf总页数
   int count = reader.numberofpages;

   textfield fielddate = new textfield(stamp.writer, new itextsharp.text.rectangle(105, 100, 240, 125), "date");
   fielddate.backgroundcolor = basecolor.white;
   fielddate.borderwidth = 1;
   fielddate.bordercolor = basecolor.black;
   fielddate.borderstyle = 4;
   fielddate.fontsize = 11f;

   textfield fieldsign = new textfield(stamp.writer, new itextsharp.text.rectangle(430, 100, 530, 125), "sign");
   fieldsign.backgroundcolor = basecolor.white;
   fieldsign.borderwidth = 1;
   fieldsign.bordercolor = basecolor.black;
   fieldsign.borderstyle = 4;
   fieldsign.fontsize = 11f;

   chunk cname = new chunk("date:", fontfactory.getfont("futura", 16f,new basecolor(170,64,0)));
   chunk ctitle = new chunk("user sign:", fontfactory.getfont("futura", 16f, new basecolor(0, 128, 128)));
   phrase pname = new phrase(cname);
   phrase ptitle = new phrase(ctitle);

   //pdfcontentbye类，用来设置图像和文本的绝对位置
   pdfcontentbyte over = stamp.getovercontent(count);
   columntext.showtextaligned(over, element.align_center, pname, 400, 420, 0);
   columntext.showtextaligned(over, element.align_center, ptitle, 400, 350, 0);

   stamp.addannotation(fielddate.gettextfield(), count);
   stamp.addannotation(fieldsign.gettextfield(), count);

   stamp.formflattening = true; 

   stamp.close();
}