怎么用c创建一个pdf文档

要用C语言创建PDF文档，你可以使用一个名为libHaru的开源库。以下是一个简单的例子，演示如何使用libHaru创建一个包含一些文本和图形的PDF文档：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "hpdf.h"

void error_handler(HPDF_STATUS error_no, HPDF_STATUS detail_no, void *user_data) {
    printf("Error: %04X, detail_no=%u\n", (unsigned int) error_no, (unsigned int) detail_no);
    exit(-1);
}

int main(int argc, char **argv) {
    HPDF_Doc pdf;
    HPDF_Page page;
    HPDF_Font font;
    HPDF_REAL tw;
    HPDF_REAL height;
    HPDF_REAL width;
    HPDF_REAL x;
    HPDF_REAL y;
    HPDF_STATUS status;
    const char *font_name = "Helvetica-Bold";
    const char *text = "Hello, world!";
    const char *file_name = "example.pdf";

    pdf = HPDF_New(error_handler, NULL);
    if (!pdf) {
        printf("Error: cannot create PDF object.\n");
        return -1;
    }

    status = HPDF_SetCompressionMode(pdf, HPDF_COMP_ALL);
    if (status != HPDF_OK) {
        printf("Error: cannot set compression mode.\n");
        HPDF_Free(pdf);
        return -1;
    }

    status = HPDF_SetEncryptionMode(pdf, HPDF_ENCRYPT_R3, 16);
    if (status != HPDF_OK) {
        printf("Error: cannot set encryption mode.\n");
        HPDF_Free(pdf);
        return -1;
    }

    status = HPDF_SetPassword(pdf, "password", "owner_password");
    if (status != HPDF_OK) {
        printf("Error: cannot set password.\n");
        HPDF_Free(pdf);
        return -1;
    }

    font = HPDF_GetFont(pdf, font_name, NULL);
    if (!font) {
        printf("Error: cannot get font.\n");
        HPDF_Free(pdf);
        return -1;
    }

    height = HPDF_Page_GetHeight(page);
    width = HPDF_Page_GetWidth(page);

    page = HPDF_AddPage(pdf);
    HPDF_Page_SetSize(page, HPDF_PAGE_SIZE_LETTER, HPDF_PAGE_PORTRAIT);
    HPDF_Page_SetTextLeading(page, 20);
    HPDF_Page_SetGrayFill(page, 0.5);
    HPDF_Page_SetFontAndSize(page, font, 24);
    tw = HPDF_Page_TextWidth(page, text);
    x = (width - tw) / 2;
    y = height - 50;
    HPDF_Page_BeginText(page);
    HPDF_Page_MoveTextPos(page, x, y);
    HPDF_Page_ShowText(page, text);
    HPDF_Page_EndText(page);

    HPDF_Page_SetLineWidth(page, 1.0);
    HPDF_Page_SetGrayStroke(page, 0.5);
    HPDF_Page_Rectangle(page, 50, 50, width - 100, height - 100);
    HPDF_Page_Stroke(page);

    status = HPDF_SaveToFile(pdf, file_name);
    if (status != HPDF_OK) {
        printf("Error: cannot save PDF file.\n");
        HPDF_Free(pdf);
        return -1;
    }

    HPDF_Free(pdf);
    return 0;
}

这段代码会创建一个包含一些文本和矩形的PDF文档，其中文本是居中对齐的，而矩形则在页面的中心。