Not able to process and write pdf file from PDF response in java

I am trying to convert a docx into pdf, microsoft graph already provides a functionality for that but thing is I am getting a PDF in response with content type "application/pdf" as a string/text from microsoft graph. I know the response is correct as the PDF is visible correctly in Postman but when I try to write it to a file manually in java code I am not able to do it properly.

I am able to create a PDF file of correct number of pages but the pdf has all blank pages.

the response body has text something like this:

%PDF-1.7
%����
1 0 obj
<</Type/Catalog/Pages 2 0 R/Lang(en) /StructTreeRoot 466 0 R/Outlines 420 0 R/MarkInfo<</Marked true>>/Metadata 3921 0 R/ViewerPreferences 3922 0 R>>
endobj
2 0 obj
<</Type/Pages/Count 135/Kids[ 3 0 R 15 0 R 19 0 R 25 0 R 26 0 R 29 0 R 31 0 R 32 0 R 33 0 R 36 0 R 37 0 R 38 0 R 40 0 R 42 0 R 43 0 R 44 0 R 45 0 R 46 0 R 47 0 R 48 0 R 49 0 R 50 0 R 51 0 R 52 0 R 53 0 R 54 0 R 55 0 R 56 0 R 57 0 R 58 0 R 59 0 R 60 0 R 61 0 R 62 0 R 63 0 R 64 0 R 65 0 R 66 0 R 67 0 R 68 0 R 69 0 R 70 0 R 71 0 R 72 0 R 73 0 R 74 0 R 75 0 R 76 0 R 77 0 R 78 0 R 79 0 R 80 0 R 81 0 R 82 0 R 83 0 R 84 0 R 85 0 R 86 0 R 87 0 R 88 0 R 89 0 R 90 0 R 91 0 R 92 0 R 93 0 R 94 0 R 95 0 R 96 0 R 97 0 R 98 0 R 99 0 R 100 0 R 101 0 R 102 0 R 103 0 R 104 0 R 105 0 R 106 0 R 107 0 R 108 0 R 109 0 R 110 0 R 111 0 R 112 0 R 113 0 R 114 0 R 115 0 R 116 0 R 117 0 R 118 0 R 119 0 R 120 0 R 121 0 R 122 0 R 123 0 R 124 0 R 125 0 R 126 0 R 127 0 R 128 0 R 129 0 R 130 0 R 131 0 R 132 0 R 133 0 R 134 0 R 135 0 R 136 0 R 137 0 R 138 0 R 139 0 R 140 0 R 141 0 R 142 0 R 143 0 R 144 0 R 145 0 R 146 0 R 147 0 R 148 0 R 149 0 R 150 0 R 151 0 R 152 0 R 153 0 R 154 0 R 155 0 R 156 0 R 157 0 R 159 0 R 161 0 R 166 0 R 170 0 R 171 0 R 172 0 R] >>
endobj
3 0 obj
<</Type/Page/Parent 2 0 R/Resources<</Font<</F1 5 0 R/F2 9 0 R>>/ExtGState<</GS7 7 0 R/GS8 8 0 R>>/XObject<</Image11 11 0 R/Image13 13 0 R>>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<</Type/Group/S/Transparency/CS/DeviceRGB>>/Tabs/S/StructParents 0>>
endobj
4 0 obj
<</Filter/FlateDecode/Length 702>>
stream
x���Qo�0�ߑ��h��`� U����2-R�0���Mi�D�����~g�6�   +Mh"Y`|�w�;�=YU�]<����=��x~��•�=��{/�<��"wg�7����ķ�������-�Q�%h!����༞\%�����y�0�-��c���Иk4��1����|�a�`[,�`}vn[W�k����)��|>�̣�o�u��h+��5��p"D������N[�f�ˏ�/�2��

MY code:

            response= rest.get(url){
                header "Authorization", "Bearer "+updateBulkPublishPdfDetailsData.sharepointAccessToken
            }
RestResponse resp=sharepointUploadSummaryResponse.getResponseEntity()
            if(resp.getHeaders().getContentType().toString()=="application/pdf"){
                String pdfString=resp.body;
                FileOutputStream out = new FileOutputStream(new File("C:\\Users\\faizanahemad.shaikh\\Downloads\\abcd.pdf"));
                out.write(pdfString.getBytes());
                out.flush();
                out.close();
            }

Basically I am using groovy grails but java solution will work, I also tried all the available solutions like receiving it as blob or directly receiving it as bytearray or converting it to inputstream and writing it but none of them worked, funny thing is I know I am receiving correct response as I am able to download it well from postman.

Also I did notice the size of file created from response is a bit more in postman like slightly more for eg: the file I create has size 1487 KB but the file I download from postman has 1563 KB and thing is both postman and my app receives same size of data, content-length is same for both: 1599780

Response:

I know I am making some mistake in processing and writing the file

I wasn't able to find a exact solution but as I wanted to convert docx to PDF via the Micorsoft Graph, I was able to resolve it by using Microsoft Graph Java SDK. Using Microsoft Graph SDK I was able to get the converted PDF file as a InputStream and was able to get all the data perfectly.

//targetFormat is "pdf"
public static byte[] downloadConvertedFile(GraphServiceClient<Request> graphClient, String fileId, String targetFormat) throws IOException, ClientException {
        try {
            InputStream stream = graphClient
                    .customRequest("/drives/" + driveId + "/items/" + fileId + "/content", InputStream.class)
                    .buildRequest(new QueryOption("format", targetFormat))
                    .get()
            if (stream != null) {
                return IOUtils.toByteArray(stream)
            }
        }catch(Exception ex){
            throw new IOException("Failed to read file from response");
        }
    }